codeforces水题100道 第二十题 Codeforces Round #191 (Div. 2) A. Flipping Game (brute force)

题目链接：http://www.codeforces.com/problemset/problem/327/A
题意：你现在有n张牌，这些派一面是0，另一面是1。编号从1到n，你需要翻转[i,j]区间的牌一次，使得看到的牌是1的数量最大。
C++代码：

#include <iostream>
using namespace std;
const int maxn = ;
int n, a[maxn], sum[maxn];
int flip(int L, int R)
{
    int a1 = sum[R] - sum[L-];
    int a2 = R - L +  - a1;
    //cout << "a1=" << a1 << "; a2=" << a2 << ";[" << L << ", " << R << "] == " << sum[n] - sum[R] + sum[L-1] + a2 << endl;
    return sum[n] - sum[R] + sum[L-] + a2;
}
int main()
{
    cin >> n;
    for (int i = ; i <= n; i ++)
    {
        cin >> a[i];
        sum[i] = sum[i-] + a[i];
    }
    int ans = min(sum[n]+, n-);
    for (int i = ; i <= n; i ++)
        for (int j = i; j <= n; j ++)
            ans = max(ans, flip(i, j));
    cout << ans;
    return ;
}

C++