搜索：zoj 2734 Exchange Cards(DFS)
【转】http://blog.csdn.net/zxy_snow/article/details/6005768
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#include <stdio.h>#include <stdlib.h>#include <iostream>#include <string.h>using namespace std;int sum,ways;int num[1010];int value,n;void DFS(int x){if( sum == value ){ways++;return ;}for(int i=x; i<=value; i++){if( num[i] && sum + i <= value ){num[i]--;sum += i;DFS(i);num[i]++;sum -= i;}}}int main(void){int x,y;int pe = 0;while( cin >> value >> n ){if( pe )cout << endl;pe = 1;memset(num,0,sizeof(num));sum = ways = 0;for(int i=0; i<n; i++){cin >> x >> y;num[x] = y;}DFS(1);cout << ways << endl;}return 0;}?