POJ1306 Combinations

思考：组合数的递推公式。

#include <iostream>#include <cstdio>#include <algorithm>using namespace std;const int maxn = 110;unsigned long long c[maxn][maxn];void work(){for(int i = 0; i < 101; i++){ c[i][0] = 1; c[i][i] = 1;}for(int i = 2; i < 101; i++) {for(int j = 1; j < i; j++) {c[i][j] = c[i-1][j] + c[i-1][j-1];}}}int main(){work();int n, m;while(scanf("%d%d", &n, &m) != EOF) {if(n == 0 && m == 0) break;else {printf("%d things taken %d at a time is %lld exactly.\n", n, m, c[n][m]);}}return 0;}