Edit Distance

Hacktoberfest2022/EditDistance.java

@@ -0,0 +1,75 @@
+import java.util.*;
+
+public class EditDistance{
+
+    public static void main(String [] args){
+         String word1="horse";
+         String word2="ros";
+         System.out.println(minimumDistanceRecursion(word1,word2,0,0));
+         System.out.println(minimumDistance(word1,word2));
+    }
+
+    public static int minimumDistanceRecursion(String word1,String word2,int idx1,int idx2){
+    	// If first string is empty, the only option is to
+        // insert all characters of second string into first
+        if(idx1==word1.length()){
+            return word2.length()-idx2;
+        }
+
+        // If second string is empty, the only option is to
+        // remove all characters of first string
+
+        if(idx2==word2.length()){
+            return word1.length()-idx1;
+        }
+
+        // If current characters of two strings are same,
+        // Ignore the characters and get count for remaining strings.
+        if (word1.charAt(idx1) == word2.charAt(idx2))
+            return minimumDistanceRecursion(word1, word2, idx1+1, idx2+1);
+
+         //If the current characters are not same
+         //return 1+minimum of all operations
+         //insert,replace,delete
+        return 1+ Math.min(minimumDistanceRecursion(word1,word2,idx1+1,idx2),
+                            Math.min(minimumDistanceRecursion(word1,word2,idx1,idx2+1),
+                                     minimumDistanceRecursion(word1,word2,idx1+1,idx2+1)));
+    }
+
+    //using dynamic programming
+    //Time Complexity: O(n*m)
+    //Space Complexity: O(n*m)
+    public static int minimumDistance(String word1, String word2) {
+        int n=word1.length(),m=word2.length();
+        int [][]dp=new int[n+1][m+1];
+        for(int i=n;i>=0;i--){
+            for(int j=m;j>=0;j--){
+                if(i==n&&j==m){
+                    dp[i][j]=0;
+                }
+                else if(i==n){
+                    dp[i][j]=m-j;
+                }
+                else if(j==m){
+                    dp[i][j]=n-i;
+                }
+                else{
+                    //if current characters are same
+                    if(word1.charAt(i)==word2.charAt(j)){
+                        dp[i][j]=dp[i+1][j+1];
+                    }
+                    else{
+                        //If current characters are different
+                        //1+minimum of all insert,delete,replace operations
+                        dp[i][j]=Math.min(dp[i+1][j],
+                                          Math.min(dp[i+1][j+1],dp[i][j+1]))
+                                          +1;   
+                    }
+                }
+            }
+        }
+        return dp[0][0];
+    }
+
+
+}