EditDistance.java

package com.fishercoder.solutions;

/**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*/
public class EditDistance {

    public int minDistance(String word1, String word2) {
        int m = word1.length(), n = word2.length();
        if(m == 0) return n;
        if(n == 0) return m;
        
        char[] str1 = word1.toCharArray();
        char[] str2 = word2.toCharArray();
        
        int[][] table = new int[m+1][n+1];
        for(int i = 0; i < m+1; i++) table[i][0] = i;
        for(int j = 0; j < n+1; j++) table[0][j] = j;
        
        for(int i = 1; i < m+1; i++){
            for(int j = 1; j < n+1; j++){
                int cost = 0;
                if(str1[i-1] != str2[j-1]) cost = 1;
                table[i][j] = Math.min(Math.min(table[i-1][j]+1, table[i][j-1]+1), table[i-1][j-1]+cost);
            }
        }
        
        return table[m][n];
    }

}