Given two strings word1 and word2, return the minimum number of operations required to convert word1 to word2.

You have the following three operations permitted on a word:


Test Cases

Example 1:

Input: word1 = "horse", word2 = "ros"
Output: 3
Explanation: 
horse -> rorse (replace 'h' with 'r')
rorse -> rose (remove 'r')
rose -> ros (remove 'e')

Example 2:

Input: word1 = "intention", word2 = "execution"
Output: 5
Explanation: 
intention -> inention (remove 't')
inention -> enention (replace 'i' with 'e')
enention -> exention (replace 'n' with 'x')
exention -> exection (replace 'n' with 'c')
exection -> execution (insert 'u')

Solution

class Solution {
public:
    int minDistance(string word1, string word2) {
        int n1 = word1.length(), n2 = word2.length();
        vector<vector<int>> dp(n1+1, vector<int>(n2+1, 0));
        for (int i = 1; i <= n1; i++) {
            dp[i][0] = i;
        }
        for (int j = 1; j <= n2; j++) {
            dp[0][j] = j;
        }
        for(int i=1; i<=n1; i++) {
            for(int j=1; j<=n2; j++) {
                if (word1[i-1] != word2[j-1]) {
                    dp[i][j] = 1 + min(dp[i-1][j-1], min(dp[i-1][j], dp[i][j-1]));
                } else {
                    dp[i][j] = dp[i-1][j-1];
                }
            }
        }
        return dp[n1][n2];
    }
};
class Solution {
    public int minDistance(String word1, String word2) {
        int n1 = word1.length(), n2 = word2.length();
        int[][] dp = new int[n1+1][n2+1];
        for (int i = 1; i <= n1; i++) {
            dp[i][0] = i;
        }
        for (int j = 1; j <= n2; j++) {
            dp[0][j] = j;
        }
        for(int i=1; i<=n1; i++) {
            for(int j=1; j<=n2; j++) {
                if (word1.charAt(i-1) != word2.charAt(j-1)) {
                    dp[i][j] = 1 + Math.min(dp[i-1][j-1], Math.min(dp[i-1][j], dp[i][j-1]));
                } else {
                    dp[i][j] = dp[i-1][j-1];
                }
            }
        }
        return dp[n1][n2];
    }
}
Time Complexity: O(nm)
Space Complexity: O(nm)