CROCMBTU 2012, Elimination Round (ACMICPC) E. Mishap in Club 夜

http://codeforces.com/contest/245/problem/E

枚举任意段内　‘＋’个数和‘－’个数的差(绝对值)　取最大

可以 O(n^2)

代码：

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#include<vector>
#include<set>
#include<map>
#include<string>
#include<queue>
#include<stack>
#include <iomanip>
using namespace std;
#define LL long long
const int INF=0x3f3f3f3f;

int main()
{
    //freopen("data.in","r",stdin);
    string s;
    while(cin>>s)
    {
        int ans=0;
        int n=s.size();

        for(int i=0;i<n;++i)
        {
            int sum1=0;
            int sum2=0;
            for(int j=i;j<n;++j)
            {
                if(s[j]=='+')
                ++sum1;
                else
                ++sum2;
                ans=max(ans,abs(sum1-sum2));
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}