21.编辑距离

class Solution {
public:
    int minDistance(string word1, string word2) {
        int n1=word1.size(),n2=word2.size();
        int dp[n1+1][n2+1];
        for(int i=0;i<=n1;i++){
            dp[i][0]=i;
        }
        for(int i=0;i<=n2;i++){
            dp[0][i]=i;
        }
        for(int i=1;i<=n1;i++)for(int j=1;j<=n2;j++){
            if(word1[i-1]==word2[j-1]){dp[i][j]=dp[i-1][j-1];}
            else dp[i][j]=min(dp[i-1][j-1],min(dp[i][j-1],dp[i-1][j]))+1;
        }
        return dp[n1][n2];
    }
};