九度 1376 最近零子序列

http://ac.jobdu.com/problem.php?id=1376

N^2的算法超时

优化算法想了好久没想出来，就当是学习一下STL的set了吧

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <set>
#include <iostream>
#define INF 0x7fffffff
using namespace std;
set<long long> S;
long long a,aa,aaa;
void check(long long x,long long &y)
{
    if(abs(x)<abs(y)){
        y=x;
    }else if(abs(x)==abs(y)&&x>=0){
        y=x;
    }
}
int main()
{
    int N,ans=INF;
    while(scanf("%d",&N)!=EOF){
        aa=0;
        int i;
        S.clear();
        cin>>a;
        S.insert(a);
        long long ans=a;
        for(i=1;i<N;i++){
            cin>>aa;
            a+=aa;
            check(a,ans);
            set<long long>::iterator it;
            it=S.lower_bound(a);
            if(it==S.end()){
                aaa=a-*S.rbegin();
                check(aaa,ans);
            }else{
                aaa=a-*it;
                check(aaa,ans);
                it--;
                aaa=a-*it;
                check(aaa,ans);
            }
            S.insert(a);
        }
        printf("%ld\n",ans);
    }
}