[LeetCode] Edit Distance

Problem:

Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)

You have the following 3 operations permitted on a word:

a) Insert a character
b) Delete a character
c) Replace a character

Solution:O(m*n)

public class Solution {
    public int minDistance(String word1, String word2) {
        if(word1.equals(word2))

            return 0;

        if(word1.length() == 0)
            return word2.length();
        if(word2.length() == 0)
            return word1.length();
        
        if(word1.length() == 1 && word2.length() == 1)
            return 1;
        
        int len1 = word1.length();
        int len2 = word2.length();
        int [][] f = new int[len1+1][len2+1];
  
        for(int i=0; i<= len1;i++){
            for(int j=0; j<= len2;j++){
                if(i == 0){
             f[i][j] = j;
                }else if(j == 0){
                    f[i][j] = i;
                }else if(word1.charAt(i-1) == word2.charAt(j-1)){
                    f[i][j] = f[i-1][j-1];
                }else{
                    f[i][j] = Math.min(f[i-1][j-1], Math.min(f[i-1][j], f[i][j-1]))+1;
                }
            }
        }
        return f[len1][len2];
    }
}

Key Concept: DP classic