euler50.myr


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use std

var primes: int[100000]
var nprimes: int

const sieve = {
	nprimes = 1
	primes[0] = 2

	for var i = 3; i < 1_000_000; i++
		for var j = 0; j < nprimes; j++
			if i % primes[j] == 0
				break
			;;
			if primes[j] * primes[j] > i
				primes[nprimes] = i
				nprimes++
				break
			;;
		;;
	;;
}

const isprime = {n
	for var i = 0; i < nprimes; i++
		if n % primes[i] == 0
			-> false
		;;
		if (primes[i]*primes[i] > n)
			-> true
		;;
	;;
	-> false
}

const prime_terms = {n, limit
	var L = n / limit
	var i = 0
	var j = 0
	var sum = 0

	while primes[i] < L
		/* calculate a[i..j] */
		while sum < n
			sum += primes[j]
			if sum == n
				-> j - i + 1
			;;
			j++
		;;
		/* calculate a[i..j-1] */
		while sum > n
			sum -= primes[i]
			i++
			if sum == n
				-> j - i
			;;
		;;
	;;
	-> 0
}

const main = {
	sieve()
	std.put("{} primes below 1000000\n", nprimes)
	var maxL = 21
	var ans = 953
	for var i = 954; i < 1_000_000; i++
		if !isprime(i)
			continue
		;;
		var pt = prime_terms(i, maxL)
		if pt > maxL
			maxL = pt
			ans = i
		;;
	;;
	std.put("len = {} ans = {}\n", maxL, ans)
}