标签:c++ project euler 质数生成
The smallest number expressible as the sum of a prime square, prime cube, and prime fourth power is 28. In fact, there are exactly four numbers below fifty that can be expressed in such a way:
28 = 22 + 23 + 24
33 = 32 + 23 + 24
49 = 52 + 23 + 24
47 = 22 + 33 + 24
How many numbers below fifty million can be expressed as the sum of a prime square, prime cube, and prime fourth power?
先判断数的大致范围:sqrt(50000000)=7081
求出2~7081之间的所有质数
然后三层循环便利出所有能表示出的50000000以内的整数
#include <iostream> #include <string> #include <map> using namespace std; bool isPrime[7081]; int prime[2000]; void judge() { for (int i = 2; i < 7081; i++) { if (isPrime[i]) { for (int j = i; j*i < 7081; j++) isPrime[j*i] = 0; } } } int getPrime() { int count = 0; for (int i = 2; i < 7081; i++) { if (isPrime[i]) { prime[count++] = i; } } return count; } int main() { memset(isPrime, true, sizeof(isPrime)); judge(); int num = getPrime(); map<int, int>mp; for (int i = 0; i < num; i++) { int a = prime[i] * prime[i] * prime[i] * prime[i]; if (a>50000000) break; for (int j = 0; j < num; j++) { int b = prime[j] * prime[j] * prime[j]; if (a + b>50000000) break; for (int k = 0; k < num; k++) { int c = prime[k] * prime[k]; if (a + b + c>50000000) break; mp[a + b + c]++; } } } cout << mp.size() << endl; system("pause"); return 0; }
版权声明:本文为博主原创文章,未经博主允许不得转载。
Project Euler:Problem 87 Prime power triples
标签:c++ project euler 质数生成
原文地址:http://blog.csdn.net/youb11/article/details/47028375