POJ 3276 Face The Right Way

#include <iostream>
#include <map>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <vector>
#include <set>

using namespace std;
#define maxn 5000 + 10
#define INF 0x7ffffff

int n;
int a[maxn];
int f[maxn];   ///区间[i, i+k-1]是否进行反转
int mark;

int Cal(int k)
{
    memset(f, 0, sizeof(f));
    int res = 0;
    int sum = 0;   ///每次使得sum的值为(i-k+1 ~ i-1)的f[i]的和
    for(int i=1; i<=n-k+1; i++)
    {
        if((sum&1) && a[i])
        {
            f[i]++;
            res++;
        }
        if(!(sum&1) && !a[i])
        {
            f[i]++;
            res++;
        }
        sum += f[i];
        if(i-k+1 > 0) sum -= f[i-k+1];
    }

    for(int i=n-k+2; i<=n; i++)
    {
        if((sum + a[i]) % 2 == 0)
        {
            return INF;
            break;
        }

        if(i-k+1 > 0)
            sum -= f[i-k+1];
    }
    return res;
}

void solve()
{
    mark = -1;
    int Min = INF;

    for(int k=1; k<=n; k++)
    {
        int tmp = Cal(k);
        if(tmp < Min)
        {
            Min = tmp;
            mark = k;
        }
    }

    cout<<mark<<" "<<Min<<endl;
}

int main()
{
    while(~scanf("%d", &n))
    {
        char ch;
        for(int i=1; i<=n; i++)
        {
            getchar();
            scanf("%c", &ch);
            if(ch == 'F') a[i] = 1;
            else a[i] = 0;
        }
        solve();
    }
    return 0;
}