initial commit

28 files changed, 1012 insertions, 0 deletions

diff --git a/euler10.c b/euler10.c
new file mode 100644
index 0000000..7d9d16b
--- /dev/null
+++ b/euler10.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#define MAX 2000000
+
+int table[MAX+1]={0};
+int primes[MAX];
+
+int main()
+{
+	int nPrimes,i,j;
+	long long sum=0;
+	for (i=2;i<=MAX;++i){
+		if (table[i]==0){
+			primes[nPrimes]=i;
+			nPrimes++;
+			sum+=i;
+		}
+		//sieve
+		for (j=2;j<=primes[nPrimes-1];++j){
+			if (i*j>MAX)
+				break;
+			else
+				table[i*j]=1;
+		}
+	}
+	printf("%lld\n",sum);
+	return 0;
+}
+
+
diff --git a/euler10.scm b/euler10.scm
new file mode 100644
index 0000000..3ae17f2
--- /dev/null
+++ b/euler10.scm
@@ -0,0 +1,13 @@
+(load "../sicp/chapter01/miller-rabin.scm")
+
+(define (sum-primes limit)
+ (define (sum-iter s l)
+  (cond ((>= l limit) s)
+   		((prime? l 5)
+		 (sum-iter (+ s l) (+ l 2)))
+		(else (sum-iter s (+ l 2)))))
+ (sum-iter 2 3))
+
+(display (sum-primes (read)))
+(newline)
+(exit)
diff --git a/euler102.c b/euler102.c
new file mode 100644
index 0000000..272a54a
--- /dev/null
+++ b/euler102.c
@@ -0,0 +1,72 @@
+#include <stdio.h>
+#include <stdbool.h>
+
+typedef struct
+{
+	int a[2],b[2],c[2];
+} triangle;
+
+static inline void
+vsub(int d[], int s[], int t[])
+{
+	d[0] = s[0] - t[0];
+	d[1] = s[1] - t[1];
+}
+
+static int
+ext_product(int s[], int t[])
+{
+	return s[0] * t[1] - s[1] * t[0];
+}
+
+static int sign(int x)
+{
+	if (x < 0)
+		return -1;
+	if (x > 0)
+		return 1;
+	return 0;
+}
+
+bool o_in_tri(triangle *t)
+{
+	int ab[2], ac[2], bc[2];
+
+	vsub(ab, t->b, t->a);
+	vsub(ac, t->c, t->a);
+	vsub(bc, t->c, t->b);
+
+	/* sig(ABxAC) = sig(OBxOC) */
+	int sabc = sign(ext_product(ab, ac));
+	int sobc = sign(ext_product(t->b, t->c));
+	if (sabc != sobc)
+		return false;
+
+	/* sig(BAxBC) = sig(OAxOC) */
+	int sbac = sign(ext_product(bc, ab));
+	int soac = sign(ext_product(t->a, t->c));
+	if (sbac != soac)
+		return false;
+
+	/* sig(CAxCB) = sig(OAxOB) */
+	int scab = sign(ext_product(ac, bc));
+	int soab = sign(ext_product(t->a, t->b));
+	if (scab != soab)
+		return false;
+
+	return true;
+}
+
+int main()
+{
+	triangle t;
+	int n = 0;
+	/* the data uses ',' to split the integers, process it with
+	 * sed 's/,/ /g' first. */
+	while (scanf("%d%d%d%d%d%d", &t.a[0], &t.a[1], &t.b[0], &t.b[1],
+				&t.c[0], &t.c[1]) != EOF) {
+		if (o_in_tri(&t))
+			n++;
+	}
+	printf("%d\n", n);
+}
diff --git a/euler11.c b/euler11.c
new file mode 100644
index 0000000..ea43b48
--- /dev/null
+++ b/euler11.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#define MAX 20
+
+int grid[MAX][MAX];
+int biggest[MAX][MAX];
+
+int main()
+{
+	int i,j,M=0;
+	for (i=0;i<MAX;++i){
+		for (j=0;j<MAX;++j){
+			scanf("%d",&grid[i][j]);
+		}
+	}
+	for (i=0;i<MAX;++i){
+		for (j=0;j<MAX;++j){
+			int p;
+			biggest[i][j]=0;
+			if (i<MAX-3){
+				p = grid[i][j]*grid[i+1][j]*grid[i+2][j]*grid[i+3][j];
+			}
+			if (j<MAX-3){
+				p = grid[i][j]*grid[i][j+1]*grid[i][j+2]*grid[i][j+3];
+				if (p>biggest[i][j])
+					biggest[i][j]=p;
+				if (i<MAX-3){
+					p = grid[i][j]*grid[i+1][j+1]*
+						grid[i+2][j+2]*grid[i+3][j+3];
+					if (p>biggest[i][j])
+						biggest[i][j]=p;
+				}
+				if (i>=3){
+					p = grid[i][j]*grid[i-1][j+1]*
+						grid[i-2][j+2]*grid[i-3][j+3];
+					if (p>biggest[i][j])
+						biggest[i][j]=p;
+				}
+			}
+			if (biggest[i][j]>M)
+				M=biggest[i][j];
+		}
+	}
+	printf("%d\n",M);
+	return 0;
+}
+			
diff --git a/euler114.scm b/euler114.scm
new file mode 100644
index 0000000..e23b441
--- /dev/null
+++ b/euler114.scm
@@ -0,0 +1,14 @@
+(define (comb m n)
+  (define (citer mm nn prod)
+    (if (> mm m) prod
+        (citer (+ mm 1) (- nn 1) (/ (* prod nn) mm))))
+  (citer 1 n 1))
+
+(define (solve nn)
+  (define (addto m n)
+    (if (> m n) 0
+        (+ (comb m n) (addto (+ m 2) (- n 2)))))
+  (+ 1 (addto 2 (- nn 1))))
+
+(display (solve 50))
+(newline)
diff --git a/euler12.scm b/euler12.scm
new file mode 100644
index 0000000..e0d726f
--- /dev/null
+++ b/euler12.scm
@@ -0,0 +1,41 @@
+(define (square x) (* x x))
+(define (power x n)
+ (if (= n 0)
+  1
+  (* x (power x (- n 1)))))
+
+(define (first-divisor x)
+ (define (try-iter d)
+  (cond ((= 0 (remainder x d)) d)
+   		((> (square d) x) x)
+		(else (try-iter (+ d 1)))))
+ (try-iter 2))
+
+(define (divexp x d)
+ (if (= (remainder x d) 0)
+	(+ (divexp (/ x d) d) 1)
+	0))
+	
+(define (ndiv n)
+ (define (pair d)
+  (cons (divexp n d) (/ n (expt d (divexp n d)))))
+ (if (= n 1) 1
+  (let ((fd (first-divisor n)))
+   (* (+ 1 (car (pair fd)))
+     (ndiv (cdr (pair fd)))))))
+
+(define (kth-factor-triangle-over-n n)
+ (define (n-fac-tri n)
+  (if (even? n)
+   (* (ndiv (/ n 2)) (ndiv (+ n 1)))
+   (* (ndiv n) (ndiv (/ (+ n 1) 2)))))
+ (define (try-iter i)
+  (if (> (n-fac-tri i) n)
+   i
+   (try-iter (+ i 1))))
+ (try-iter 1))
+
+(display 
+ ((lambda (x) (/ (* x (+ x 1)) 2))
+  (kth-factor-triangle-over-n 500)))
+(newline)
diff --git a/euler13.scm b/euler13.scm
new file mode 100644
index 0000000..f4246e9
--- /dev/null
+++ b/euler13.scm
@@ -0,0 +1,104 @@
+(display
+  (+
+	371072875339
+	463769376774
+	743249861995
+	919422133635
+	230675882075
+	892616706966
+	281128798128
+	442742289174
+	474514457360
+	703864861058
+	621764571418
+	649063524627
+	925758677183
+	582035653253
+	801811993848
+	353986643728
+	865155060062
+	716938887077
+	543700705768
+	532826541087
+	361232725250
+	458765761724
+	174237069058
+	811426604180
+	519343254517
+	624672216484
+	157324443869
+	550376875256
+	183363848253
+	803862875928
+	781828337579
+	167263201004
+	484030981290
+	870869875513
+	599594068957
+	697939506796
+	410526847082
+	653786073615
+	358290353174
+	949537597651
+	889028025717
+	252676802760
+	362702185404
+	240744869082
+	914302881971
+	344130655780
+	230530811728
+	114876969321
+	637832994906
+	677201869716
+	955482553002
+	760853271322
+	377742425354
+	237019132757
+	297988602722
+	184957014548
+	382982037830
+	348295438291
+	409579530664
+	297461521855
+	416981162220
+	624679571944
+	231897067725
+	861880882258
+	113067397083
+	829591747671
+	976233310448
+	428462801835
+	551216035469
+	322381957343
+	755061649651
+	621778427521
+	329241857071
+	995186714302
+	732674608005
+	768418225246
+	971426179103
+	877836461827
+	108488025216
+	713296124747
+	621840735723
+	666278919814
+	606618262936
+	857869440895
+	660243964099
+	649139826800
+	167309393198
+	948093772450
+	786391670211
+	153687137119
+	407899231155
+	448899115014
+	415031288803
+	812348806732
+	826165707739
+	229188020587
+	771585425020
+	721078384350
+	208496039801
+	535035342264
+	))
+(newline)
diff --git a/euler14.scm b/euler14.scm
new file mode 100644
index 0000000..3adc07a
--- /dev/null
+++ b/euler14.scm
@@ -0,0 +1,28 @@
+(define (chainlen n)
+ (define (next m)
+  (if (even? m)
+   (/ m 2)
+   (+ (* m 3) 1)))
+ (define (count-iter cur cnt)
+  (if (= cur 1)
+   cnt
+   (count-iter (next cur) (+ cnt 1))))
+ (count-iter n 1))
+
+(define (find-max-len-start limit)
+  (define (try cur longest ans)
+	(cond ((> cur limit) ans)
+		  ((= (remainder (- cur 4) 6) 0)
+		   ;it's even and is 3n+1=>it's 6n+4
+		   (try (+ cur 1) longest ans))
+		  (else
+			(let ((len (chainlen cur))
+				  (curn (+ cur 1)))
+			  (if (> len longest)
+				(try curn len cur)
+				(try curn longest ans))))))
+ (let ((lowest (ceiling (/ limit 2))))
+  (try lowest 1 lowest)))
+
+(display (find-max-len-start 999999))
+(newline)
diff --git a/euler16.scm b/euler16.scm
new file mode 100644
index 0000000..0260783
--- /dev/null
+++ b/euler16.scm
@@ -0,0 +1,9 @@
+(define (sum-digits n)
+ (if (= n 0)
+  0
+  (+ (remainder n 10)
+   (sum-digits (floor (/ n 10))))))
+
+(display (sum-digits (expt 2 1000)))
+(newline)
+
diff --git a/euler17.c b/euler17.c
new file mode 100644
index 0000000..f6def67
--- /dev/null
+++ b/euler17.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+
+const char* num_en[]={
+	"",
+	"one", "two", "three", "four",
+	"five", "six", "seven", "eight",
+	"nine", "ten", "eleven", "twelve",
+	"thirteen", "fourteen", "fifteen", "sixteen",
+	"seventeen", "eighteen", "nineteen", "twenty",
+	"thirty", "forty", "fifty", "sixty",
+	"seventy", "eighty", "ninety"};
+
+void name_num(int num,char* name)
+{
+	name[0]=0;
+	if (num>=1000){
+		strcat(name,num_en[num/1000]);
+		strcat(name," thousand ");
+		num %= 1000;
+		if (num>0 && num<100)
+			strcat(name,"and ");
+	}
+	if (num>=100){
+		strcat(name,num_en[num/100]);
+		strcat(name," hundred ");
+		num %= 100;
+		if (num>0){
+			strcat(name,"and ");
+		}
+	}
+	if (num>20){
+		strcat(name,num_en[20-2+num/10]);
+		num %= 10;
+		if (num>0)
+			strcat(name,"-");
+		strcat(name,num_en[num%10]);
+	}else{
+		strcat(name,num_en[num]);
+	}
+}
+
+int count_letters(char* s)
+{
+	char *p;
+	int count=0;
+	for (p=s; *p; ++p){
+		if (islower(*p)){
+			++count;
+		}
+	}
+	return count;
+}
+
+int main()
+{
+	int n,i,len,total_len=0;
+	char num_en[100];
+	for (i=1;i<=1000;++i){
+		name_num(i,num_en);
+		len = count_letters(num_en);
+		total_len += len;
+		//printf("%s %d\n",num_en,len);
+	}
+	printf("%d\n",total_len);
+	return 0;
+}
diff --git a/euler18.c b/euler18.c
new file mode 100644
index 0000000..281dc77
--- /dev/null
+++ b/euler18.c
@@ -0,0 +1,43 @@
+#include <stdio.h>
+#define MAX 15
+
+int max(int i,int j)
+{
+	if (i>j)
+		return i;
+	else
+		return j;
+}
+
+int main()
+{
+	int triangle[MAX][MAX];
+	int answer[MAX][MAX];
+	int maxtotal=0;
+	int i,j;
+	for (i=0; i<MAX; ++i){
+		for (j=0; j<=i; ++j){
+			scanf("%d",&triangle[i][j]);
+			if (i==0){
+				answer[i][j]=triangle[i][j];
+			}else if (j==0){
+				answer[i][j]=
+					triangle[i][j]+answer[i-1][j];
+			}else if (j==i){
+				answer[i][j]=
+					triangle[i][j]+answer[i-1][j-1];
+			}else{
+				answer[i][j]=
+					triangle[i][j]+
+					max(answer[i-1][j-1],answer[i-1][j]);
+			}
+			if (answer[i][j]>maxtotal){
+				maxtotal=answer[i][j];
+			}
+		}
+	}
+	printf("%d\n",maxtotal);
+	return 0;
+}
+	
+
diff --git a/euler19.c b/euler19.c
new file mode 100644
index 0000000..78a9d55
--- /dev/null
+++ b/euler19.c
@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+const int days[2][12]={
+	{31,28,31,30,31,30,31,31,30,31,30,31},
+	{31,29,31,30,31,30,31,31,30,31,30,31}};
+
+int isleap(int y)
+{
+	if (y%4==0 && (y%100!=0 || y%400==0))
+		return 1;
+	else
+		return 0;
+}
+
+int main()
+{
+	int y,m,t;
+	int d=1+365,count=0;
+	for (y=1901;y<=2000;++y){
+		t=isleap(y);
+		for (m=0;m<12;++m){
+			d%=7;
+			if (d==0)
+				++count;
+			d+=days[t][m];
+		}
+	}
+	printf("%d\n",count);
+	return 0;
+}
+
diff --git a/euler2.scm b/euler2.scm
new file mode 100644
index 0000000..f47cad2
--- /dev/null
+++ b/euler2.scm
@@ -0,0 +1,10 @@
+(define (sum-fib sum a b c)
+ (if (> a 4000000)
+  sum
+  (if (even? a)
+   (sum-fib (+ sum a) b c (+ b c))
+   (sum-fib sum b c (+ b c)))))
+
+(display (sum-fib 0 1 2 3))
+(newline)
+
diff --git a/euler20.scm b/euler20.scm
new file mode 100644
index 0000000..df06c9d
--- /dev/null
+++ b/euler20.scm
@@ -0,0 +1,16 @@
+(define (sum-digits n)
+ (if (= n 0)
+  0
+  (+ (remainder n 10)
+   (sum-digits (floor (/ n 10))))))
+
+(define (! n)
+ (define (p-iter i p)
+  (if (> i n)
+   p
+   (p-iter (+ i 1) (* p i))))
+ (p-iter 1 1))
+
+(display (sum-digits (! 100)))
+(newline)
+
diff --git a/euler21.c b/euler21.c
new file mode 100644
index 0000000..d18e556
--- /dev/null
+++ b/euler21.c
@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <math.h>
+#define MAX 9999
+
+int firstdiv(int n)
+{
+	int i;
+	int q=ceil(sqrt(n));
+	for (i=2;i<=q;++i){
+		if (n%i==0)
+			return i;
+	}
+	return n;
+}
+
+int divexp(int n,int d)
+{
+	int dd=1;
+	while (n%d==0){
+		n/=d;
+		dd*=d;
+	}
+	return dd;
+}
+
+int sumdiv(int n)
+{
+	if (n==1)
+		return 1;
+
+	int fd=firstdiv(n);
+	int fdexp=divexp(n,fd);
+	return sumdiv(n/fdexp)*(fdexp*fd-1)/(fd-1);
+}
+
+int main()
+{
+	int d[MAX+1],i,sum=0;
+	for (i=1;i<=MAX;++i){
+		d[i]=sumdiv(i)-i;
+	}
+	for (i=1;i<=MAX;++i){
+		if (i<d[i] && d[i]<=MAX && i==d[d[i]]){
+			sum+=i+d[i];
+		}else if (d[i]>MAX && sumdiv(d[i])-d[i]==i){
+			sum+=i;
+		}
+	}
+	printf("%d\n",sum);
+	return 0;
+}
+	
diff --git a/euler22.c b/euler22.c
new file mode 100644
index 0000000..d969fe7
--- /dev/null
+++ b/euler22.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+int main()
+{
+	char name[10];
+	int i,j,score=0;
+	for (i=1;scanf("%s",name)!=EOF;++i){
+		int worth=0;
+		for (j=0;name[j];++j){
+			worth+=name[j]&0xbf;
+		}
+		score+=worth*i;
+	}
+	printf("%d\n",score);
+	return 0;
+}
+
diff --git a/euler23.c b/euler23.c
new file mode 100644
index 0000000..bac7b08
--- /dev/null
+++ b/euler23.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#define MAX 100000
+
+int sum_of_div(int n)
+{
+	int fd,fdsum=1,sum=1;
+	while (n%2==0){
+		fdsum<<=1;
+		n>>=1;
+	}
+	sum *= (fdsum*2-1);
+	fd = 3;
+	while (n>1){
+		fdsum=1;
+		while (n%fd==0){
+			fdsum*=fd;
+			n/=fd;
+		}
+		sum *= (fdsum*fd-1)/(fd-1);
+		fd += 2;
+	}
+	return sum;
+}
+
+int main()
+{
+	int n,i,j;
+	int abundant[MAX];
+	int sum_abundant[MAX]={0};
+	int ans=0;
+	for (i=1;i<=28123;++i){
+		if (sum_of_div(i)>i*2){
+			abundant[i]=1;
+			for (j=1;j<=i&&j<=28123-i;++j){
+				if (abundant[j]){
+					sum_abundant[i+j]=1;
+				}
+			}
+		}else{
+			abundant[i]=0;
+		}
+	}
+	for (int i=1;i<=28123;++i){
+		if (!sum_abundant[i])
+			ans+=i;
+	}
+	printf("%d\n",ans);
+}
+
diff --git a/euler26.scm b/euler26.scm
new file mode 100644
index 0000000..6c01409
--- /dev/null
+++ b/euler26.scm
@@ -0,0 +1,30 @@
+(define (recur-cycle n)
+ (define (div_2_5 x)
+  (cond 
+   ((= (remainder x 2) 0)
+	(div_2_5 (/ x 2)))
+   ((= (remainder x 5) 0)
+	(div_2_5 (/ x 5)))
+   (else x)))
+ (define (try-iter m r)
+  (if (= r 1)
+   m
+   (try-iter (+ m 1) (remainder (* r 10) n))))
+ (if (= (div_2_5 n) n)
+  (if (= n 1)
+   0
+   (try-iter 1 (remainder 10 n)))
+  (recur-cycle (div_2_5 n))))
+
+(define (longest upper)
+ (define (try-iter n ans anscycle)
+  (if (> n upper)
+   ans
+   (let ((m (recur-cycle n)))
+	 (if (> m anscycle)
+	  (try-iter (+ n 1) n m)
+	  (try-iter (+ n 1) ans anscycle)))))
+ (try-iter 1 1 0))
+
+(display (longest (read)))
+(newline)
diff --git a/euler27.c b/euler27.c
new file mode 100644
index 0000000..f2c2435
--- /dev/null
+++ b/euler27.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <stdlib.h>
+#define MAX 3000000
+
+int notPrime[MAX]={0};
+
+void genprimes(int n)
+{
+	notPrime[0]=1;
+	notPrime[1]=1;
+	int i,j;
+	for (i=2;i<=n;++i){
+		if (!notPrime[i]){
+			for (j=i*2;j<=n;j+=i){
+				notPrime[j]=1;
+			}
+		}
+	}
+}
+	
+int main()
+{
+	int a,b,n;
+	int product=0,longest=0;
+	genprimes(MAX);
+	for (a=-999;a<=999;a+=2){
+		for (b=-997;b<=997;b+=2){
+			if (notPrime[abs(b)])
+				continue;
+			for (n=0;;++n){
+				int t=(n+a)*n+b;
+				if (notPrime[abs(t)]){
+					if (n>longest){
+						longest = n;
+						product = a*b;
+					}
+					break;
+				}
+			}
+		}
+	}
+	printf("%d\n",product);
+	return 0;
+}
+
diff --git a/euler29.c b/euler29.c
new file mode 100644
index 0000000..a9e5fc5
--- /dev/null
+++ b/euler29.c
@@ -0,0 +1,31 @@
+#include <stdio.h>
+#define LIMIT 4
+
+int d[LIMIT+1][LIMIT+1]={};
+int count=(LIMIT-1)*(LIMIT-1);
+
+int main()
+{
+	int a,b,c;
+	for (a=2;a<=LIMIT;a++){
+		int bb=a;
+		for (b=2;b<=LIMIT;b++){
+			bb*=a;
+			if (bb>LIMIT) break;
+			for (c=2;c<=LIMIT/b;c++){
+				d[bb][c]=1; // (a^b)^c = a^(bc)
+			}
+		}
+	}
+	for (a=2;a<=LIMIT;a++){
+		for (b=2;b<=LIMIT;b++){
+			if (d[a][b]){
+				printf("%d %d\n",a,b);
+				--count;
+			}
+		}
+	}
+	printf("%d\n",count);
+	return 0;
+}
+
diff --git a/euler39.c b/euler39.c
new file mode 100644
index 0000000..e4cd40c
--- /dev/null
+++ b/euler39.c
@@ -0,0 +1,38 @@
+#include <stdio.h>
+
+int np(int p)
+{
+	int n = 0;
+	int a;
+
+	/* p = a + b + c, with a*a+b*b=c*c */
+	/* b = (p*p-2pa)/(2p-2a) */
+	if (p % 2 == 1)
+		return 0;
+
+	a = 1;
+	while (1) {
+		int nu = p * (p - a*2);
+		int de = (p - a) * 2;
+		if (nu % de == 0 && nu/de > a)
+			n++;
+		if (nu/de < a)
+			break;
+		a++;
+	}
+	return n;
+}
+
+int main()
+{
+	int bestp, M = 0;
+	int i;
+	for (i = 3; i<=1000; i++) {
+		int m = np(i);
+		if (m > M) {
+			bestp = i;
+			M = m;
+		}
+	}
+	printf("%d\n", bestp);
+}
diff --git a/euler4.scm b/euler4.scm
new file mode 100644
index 0000000..09408a9
--- /dev/null
+++ b/euler4.scm
@@ -0,0 +1,20 @@
+(define (palindrome? x)
+  (define (rev x ans)
+	(if (= x 0)
+	  ans
+	  (let ((r (remainder x 10)))
+	   (rev (/ (- x r) 10) (+ r (* ans 10))))))
+  (= (rev x 0) x))
+
+(define (bigpal ans x y)
+ (if (> x 999)
+  ans
+  (if (> y 999)
+   (bigpal ans (+ x 1) (+ x 1))
+   (if (and (palindrome? (* x y)) (> (* x y) ans))
+	(bigpal (* x y) x (+ y 1))
+	(bigpal ans x (+ y 1))))))
+
+(display (bigpal 0 100 100))
+(newline)
+
diff --git a/euler41.sh b/euler41.sh
new file mode 100644
index 0000000..133d894
--- /dev/null
+++ b/euler41.sh
@@ -0,0 +1,3 @@
+# Pandigital prime is at most 7 digits, because 1+...+8 and 1+...+9 is multiply of 3
+for i in 76{1..5}{1..5}{1..5}{1..5}{1,3,5} ; do factor $i; done | sed -e '/[0-9] /d' | cut -d':' -f1 \
+  | sed $(for i in {1..7} ; do printf '\x2de /%d.*%d/d ' $i $i ; done)
diff --git a/euler44.c b/euler44.c
new file mode 100644
index 0000000..db032aa
--- /dev/null
+++ b/euler44.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+long long Pn(int n)
+{
+	return (long long)n*(long long)(3*n-1)/2;
+}
+
+#define MAXSIZE (1<<22)
+long long P[MAXSIZE];
+
+int comp(const void *a, const void *b)
+{
+	long long aa = *(long long*)a;
+	long long bb = *(long long*)b;
+	if (aa < bb)
+		return -1;
+	if (aa > bb)
+		return 1;
+	return 0;
+}
+
+int main()
+{
+	int i, j;
+	int range = (1<<15);
+	for (i = 1; i < range; i++)
+		P[i] = Pn(i);
+
+	/* i < 257 is impossible when searching with range=(1<<15) */
+	/* i < 725 is impossible with range=(1<<18) */
+	/* i < 1449 is impossible with range=(1<<20) */
+	for (i = 1; i < range; i++) {
+		long long diff = P[i];
+		for (j = 1; j < range - 1; j++) {
+			long long Pj = P[j];
+			long long Pk = Pj + diff;
+			long long Pjk = Pj + Pk;
+			if (Pk < P[j+1])
+				break;
+			while (Pjk > P[range-1]) {
+				int newrange = range * 2;
+				int r;
+				for (r = range; r < newrange; r++)
+					P[r] = Pn(r);
+				range = newrange;
+			}
+			if (!bsearch(&Pk, P+1, range-1, sizeof(long long), comp))
+				continue;
+			if (!bsearch(&Pjk, P+1, range-1, sizeof(long long), comp))
+				continue;
+			printf("i = %d, D = %lld, j = %d, P[j] = %lld\n", i, diff, j, Pj);
+			/* i = 1912, D = 5482660, j = 1020, P[j] = 1560090 */
+			return 0;
+		}
+		printf("i = %d\n", i);
+	}
+}
diff --git a/euler60.c b/euler60.c
new file mode 100644
index 0000000..3bc933c
--- /dev/null
+++ b/euler60.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#define NP 10000
+
+int primetab[NP];
+
+void genprimes()
+{
+    int i=2,j;
+    primetab[0] = 2;
+    primetab[1] = 3;
+    
+    while (i<NP) {
+        primetab[i] = primetab[i-1]+2;
+        for (j=0; j<i; j++) {
+            if (primetab[i]%primetab[j]==0) {
+                // try next
+                primetab[i] += 2;
+                j=-1;
+                continue;
+            }
+        }
+        i++;
+    }
+}
+
+void search(int depth)
+{
+    static int result[5]={0,0,0,0,0}, bestsum=0;
+
+    int s=0,i;
+
+    if (depth==5) {
+        for (i=0; i<5; i++) {
+            printf("%d ", primetab[result[i]]);
+        }
+        printf("best=%d\n", bestsum);
+    }
+    
+    for (i=0; i<depth; i++) {
+        s += primetab[result[i]];
+    }
+    if (bestsum && s>bestsum) return;
+    
+    if (depth==0) {
+        result[0] = 1;
+    } else {
+        result[depth] = result[depth-1]+1;
+    }
+    if (result[depth]>=NP) {
+        return;
+    }
+    
+    while (result[depth]<NP) {
+        // check if it's ok
+    }
+            
+}
+
+int main()
+{
+    genprimes();
+    int i;
+    
+    for (i=0; i<1000; i++) {
+        printf("%d\n", primetab[i]);
+    }
+    return 0;
+}
diff --git a/euler7.scm b/euler7.scm
new file mode 100644
index 0000000..50daa8a
--- /dev/null
+++ b/euler7.scm
@@ -0,0 +1,16 @@
+(load "../sicp/chapter01/miller-rabin.scm")
+
+(define (nth-prime n)
+ (define (try-iter p nth)
+  (if (prime? p 5)
+   (if (= nth (- n 1))
+	p
+	(try-iter (+ p 2) (+ nth 1)))
+   (try-iter (+ p 2) nth)))
+ (if (= n 1) 
+  2
+  (try-iter 3 1)))
+
+(display (nth-prime (read)))
+(newline)
+(exit)
diff --git a/euler8.c b/euler8.c
new file mode 100644
index 0000000..d0581be
--- /dev/null
+++ b/euler8.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+
+int main()
+{
+	int greatest=0,t;
+	char a[1100];
+	int d[1100],i;
+	scanf("%s",a);
+	for (i=0;i<4;++i)
+		d[i]=a[i]-'0';
+	for (i=4;a[i];++i){
+		d[i]=a[i]-'0';
+		t=d[i]*d[i-1]*d[i-2]*d[i-3]*d[i-4];
+		if (t>greatest)
+			greatest=t;
+	}
+	printf("%d\n",greatest);
+	return 0;
+}
+
diff --git a/euler99.c b/euler99.c
new file mode 100644
index 0000000..e337796
--- /dev/null
+++ b/euler99.c
@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct elem
+{
+	int idx;
+	double v;
+};
+
+int comp(const void *s, const void *t)
+{
+	struct elem *ss = (struct elem*)s;
+	struct elem *tt = (struct elem*)t;
+	if (ss->v < tt->v)
+		return -1;
+	if (ss->v > tt->v)
+		return 1;
+	return 0;
+}
+
+int main()
+{
+	struct elem arr[100000];
+	int n;
+	char buffer[1000];
+
+	n = 0;
+	while (fgets(buffer, 1000, stdin)) {
+		if (strlen(buffer) < 3)
+			break;
+		int a = atoi(buffer);
+		int b = atoi(strchr(buffer, ',')+1);
+		arr[n].idx = n + 1;
+		arr[n].v = b * log(a);
+		n ++;
+	}
+	qsort(arr, n, sizeof(arr[0]), comp);
+	printf("%d\n", arr[n-1].idx);
+}