uva 10392 - Factoring Large Numbers

好水。。以至于我循环的时候都忘了开方。。。

#include <stdio.h>#include <string.h>#include <math.h>bool isPrime[1000001];long long prime[78500];long long pn = 0;void init() {memset(isPrime, true, sizeof(isPrime));for(int i = 2; i * i <= 1000000; i++) {if(isPrime[i]) {for(int j = i * i; j <= 1000000; j += i)isPrime[j] = false;}}for(int i = 2; i <= 1000000; i++)if(isPrime[i]) prime[pn++] = i;}int main() {init();long long n;while(scanf("%lld", &n) != EOF && n >= 0 ) {for(long long i = 0; i < pn; i++) {if(n == 1) break;while(n % prime[i] == 0) {printf(" %lld/n", prime[i]);n /= prime[i];}}long long m = sqrt(n + 0.5);for(long long i = prime[pn - 1] + 1; i <= m; i++) {if(n == 1) break;while(n % i == 0) {printf(" %lld/n", i);n /= i;}}if(n != 1) printf(" %lld/n", n);printf("/n");}return 0;}