LeetCode 583. 两个字符串的删除操作 (LCS、DP)

两个字符串的删除操作

class Solution {
public:
    int minDistance(string s1, string s2) {
        int n = s1.size() , m = s2.size();
        vector<vector<int>> dp(n+1,vector<int>(m+1,1e9));
        dp[0][0] = 0;
        for(int i=0;i<=n;i++){
            dp[i][0] = i;
        }
        for(int i=0;i<=m;i++){
            dp[0][i] = i;
        }
        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                if(s1[i-1]==s2[j-1]){
                    dp[i][j] = min(dp[i][j],dp[i-1][j-1]);
                }else{
                    dp[i][j] = min(dp[i-1][j],dp[i][j-1])+1;
                }
            }
        }
        return dp[n][m];        
    }
};

当然也可直接处理成LCS的问题

class Solution {
public:
    int minDistance(string word1, string word2) {
        int len = longestCommonSubsequence(word1,word2);
        return word1.size()+word2.size()-2*len;
    }
    int longestCommonSubsequence(string s1, string s2) {
        int n = s1.size() , m = s2.size();
        vector<vector<int>> dp(n+1,vector<int>(m+1,0));
        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                dp[i][j] =max(dp[i-1][j-1]+(s1[i-1]==s2[j-1]),max(dp[i][j-1],dp[i-1][j]));
            }
        }
        return dp[n][m];
    }    
};