Project Euler problem 44

来源：互联网发布：matlab矩阵赋值编辑：程序博客网时间：2024/06/03 18:42

哎。。。直接往上枚举就行了。

不过我还是加了点小的优化。。

但是很纯暴力相比感觉没优化多少。。都是O(n ^ 2)的

#include <iostream>#include <cstdio>#include <cstring>#include <ctime>#include <cstdlib>#include <stack>#include <cmath>#define eps 1e-6#define INF 1000000007#define PI acos(-1.0)using namespace std;bool ok(int x){    x = x * 12 + 1;    int m = (int)sqrt(x * 1.0);    if(m * m == x && (m + 1) % 6 == 0) return 1;    return 0;}bool gao(int x){    int m = (int)sqrt(x * 1.0);    for(int i = 2; i <= m; i++)    {        if(x % i == 0)        {            int t = x / i;            if((t + 1) % 3 != 0) continue;            if(t - 3 * i + 1 < 6) break;            int k1 = (t + 1) / 3;            int k2 = i;            if((k1 + k2) % 2 == 1 || k1 <= k2) continue;            int a = (k1 + k2) / 2;            int b = (k1 - k2) / 2;            if(ok(3 * (a * a + b * b) - a - b)) return 1;        }    }    return 0;}int main(){    for(int i = 5;  ; i++)    {        if(gao(i * (3 * i - 1)))        {            cout << i * (3 * i - 1) / 2 << endl;            break;        }    }    return 0;}