SRM 698 div1 RepeatString

250pts RepeatString

题意：问最少修改多少次将一个字符串修改为AA的形式。可以插入一个字符，删除一个字符，修改字符。

思路：枚举分界点，然后dp一下。

/*
* @Author: mjt
* @Date:   2018-10-17 19:50:16
* @Last Modified by:   mjt
* @Last Modified time: 2018-10-17 20:08:04
*/
#include<bits/stdc++.h>
using namespace std;
typedef long long LL;

const int N = 1005;

int f[N][N];

class RepeatString{
public:
    int solve(int p,string s) {
        memset(f, 0x3f, sizeof(f));
        string a, b;
        a += '#', b += '#';
        for (int i=0; i<=p; ++i) a += s[i];
        for (int j=p+1; j<(int)s.size(); ++j) b += s[j];
        for (int i=0; i<(int)a.size(); ++i) f[i][0] = i;
        for (int i=0; i<(int)b.size(); ++i) f[0][i] = i;
        
        for (int i=1; i<(int)a.size(); ++i) 
            for (int j=1; j<(int)b.size(); ++j) {
                f[i][j] = min(f[i][j], min(f[i - 1][j], f[i][j - 1]) + 1);
                f[i][j] = min(f[i][j], f[i - 1][j - 1] + (a[i] != b[j]));
            }
        return f[a.size() - 1][b.size() - 1];
    }
    int minimalModify(string s) {
        int ans = s.size();
        for (int i=0; i<(int)s.size(); ++i) ans = min(ans, solve(i, s));
        return ans - 1;
    }
};