USACO 2.2.2 Subset Sums - 小阮的菜田

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ID: lorelei3

TASK: subset

LANG: C++

#include<stdio.h>

const int N = 40;

const int MAX = (1+N)*N/4;

long long ans[N][MAX];

int main(){

int n, tot, sum;

freopen("subset.in", "r", stdin);

freopen("subset.out", "w", stdout);

scanf("%d", &n);

tot = (1+n)*n/2;

if(tot&0x01){

printf("0\n");

return 0;

}

sum = tot/2;

ans[1][0] = 1; ans[1][1] = 1;

for(int i=2; i<=n; ++i)

for(int j=0; j<=sum; ++j)

if(j-i>=0)

ans[i][j]=ans[i-1][j]+ans[i-1][j-i];

else

ans[i][j]=ans[i-1][j];

printf("%lld\n", ans[n][sum]/2);

return 0;

}

posted on 2010-11-21 00:48 小阮阅读(167) 评论(0) 编辑收藏引用所属分类: USACO

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