Edit Distance

public class Solution {
    public int minDistance(String word1, String word2) {
        if(word1==null||word1.length()==0) return word2.length();
        if(word2==null||word2.length()==0) return word1.length();
        int[][] dp = new int[word1.length()+1][word2.length()+1];
        for(int i=1;i<=word1.length();i++){
            dp[i][0]=i;
        }
        for(int j=1;j<=word2.length();j++){
            dp[0][j] = j;
        }
        for(int i=1;i<=word1.length();i++){
            char a = word1.charAt(i-1);
            for(int j=1;j<=word2.length();j++){
                if(a==word2.charAt(j-1)){
                    dp[i][j]=dp[i-1][j-1];
                }else{
                    dp[i][j]=Math.min(Math.min(dp[i-1][j-1],dp[i][j-1]),dp[i-1][j])+1;
                }
            }
        }
        return dp[word1.length()][word2.length()];
    }
}