51nod 1065 最小正子段和

题目链接：51nod 1065 最小正子段和

房教说用前缀和做,然后看了别人博客懂了后就感觉,这个真有意思...

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N = 50001;
const int inf  = 0x3f3f3f3f;
pair<long long, int> sum[N];
int a[N];
int n;
int main(){
    int i, j;
    long long ans = inf;
    scanf("%d", &n);
    sum[0] = make_pair(0,0);
    for(i = 1; i <= n; ++i){
        scanf("%d", &a[i]);
        sum[i].first = a[i] + sum[i-1].first;
        sum[i].second = i;
    }
    sort(sum+1, sum+1+n);
    for(i = 1; i <= n; ++i){
        if(sum[i].first > 0)
            ans = min(ans, sum[i].first);
        if(sum[i].second > sum[i-1].second && sum[i].first > sum[i-1].first)
            ans = min(ans, sum[i].first - sum[i-1].first);
    }
    printf("%lld\n", ans);
    return 0;
}