72. Edit Distance

1、题目描述

给两个字符串a和b，找到把a转换成b用的最少转换次数。转换方式有三种，插入，删除，替换。

2、思路

dynamic Programming.

dp[i][j] refers to the minimum number of steps required to convert a.substr(0,i) to b.substr(0,j).

If a[i]==b[j], dp[i+1][j+1] = dp[i][j];

else dp[i+1][j+1] = min(dp[i][j], dp[i+1][j], dp[i][j+1]) +1.

3、代码

    int minDistance(string word1, string word2) {        int l1 = word1.size(),l2=word2.size();        int dp[l1+1][l2+1];              for(int i=0;i<=l1;i++)            dp[i][0]=i;        for(int i=0;i<=l2;i++)            dp[0][i]=i;        for(int i=0;i<l1;i++){            for(int j=0;j<l2;j++){                if(word1[i]==word2[j])                    dp[i+1][j+1]=dp[i][j];                else{                    dp[i+1][j+1]=min(dp[i+1][j],min(dp[i][j],dp[i][j+1]))+1;                }            }        }        return dp[l1][l2];    }