递归

题目描述

Given two positive integers N and M, please divide N into several integers A1, A2, …, Ak (k >= 1), so that:

1. 0 < A1 < A2 < … < Ak;

2. A1 + A2 + … + Ak = N;

3. A1, A2, …, Ak are different with each other;

4. The product of them P = A1 * A2 * … * Ak is a multiple of M;

How many different ways can you achieve this goal?

递归解法

#include <cstdio>#include <cmath>#include <cstring>#include <algorithm>using namespace std;enum {maxn = 100+3, maxm = 50+3};//int f[maxn][maxn][maxm];int dfs(int n, int m, int last, int sum, int mul){    if (sum == n)        if (mul %m == 0)            return 1;        else            return 0;    int cnt = 0;    for (int i=last+1; i <= n -sum; i++)        cnt += dfs(n, m, i, sum+i, mul *i);    return cnt;}#define OJint main(){    #ifndef OJ    freopen("in.txt", "r", stdin);    #endif // OJ    int n, m;    scanf("%d %d", &n, &m);    printf("%d\n", dfs(n, m, 0, 0, 1));}

更好的解法：
http://hihocoder.com/discuss/question/2670