Add Edit Distance implementation

Dynamic Programming/EditDistance.java

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+/*
+  A Dynamic Programming based Java program to find minimum
+  number operations to convert str1 to str2
+*/
+class EditDistance
+{
+    // Returns the min int
+    static int min(int x,int y,int z)
+    {
+        if (x <= y && x <= z) return x;
+        if (y <= x && y <= z) return y;
+        else return z;
+    }
+
+    // Edit Distance based on DP
+    static int editDistanceDP(String str1, String str2, int m, int n)
+    {
+        // Create a table to store results of subproblems
+        int dp[][] = new int[m+1][n+1];
+
+        // Fill d[][] in bottom up manner
+        for (int i=0; i<=m; i++)
+        {
+            for (int j=0; j<=n; j++)
+            {
+                // If first string is empty, only option is to
+                // insert all characters of second string
+                if (i==0)
+                    dp[i][j] = j;  // Min. operations = j
+
+                // If second string is empty, only option is to
+                // remove all characters of second string
+                else if (j==0)
+                    dp[i][j] = i; // Min. operations = i
+
+                // If last characters are same, ignore last char
+                // and recur for remaining string
+                else if (str1.charAt(i-1) == str2.charAt(j-1))
+                    dp[i][j] = dp[i-1][j-1];
+
+                // If the last character is different, consider all
+                // possibilities and find the minimum
+                else
+                    dp[i][j] = 1 + min(dp[i][j-1],  // Insert
+                                       dp[i-1][j],  // Remove
+                                       dp[i-1][j-1]); // Replace
+            }
+        }
+
+        return dp[m][n];
+    }
+
+
+
+    public static void main(String args[])
+    {
+        String str1 = "their";
+        String str2 = "they're";
+        System.out.println( editDistanceDP( str1 , str2 , str1.length(), str2.length()) );
+    }
+}

Dynamic Programming/EditDistance/Java/EditDistance.java

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+/*
+  A Dynamic Programming based Java program to find minimum
+  number operations to convert str1 to str2
+*/
+class EditDistance
+{
+    // Returns the min int
+    static int min(int x,int y,int z)
+    {
+        if (x <= y && x <= z) return x;
+        if (y <= x && y <= z) return y;
+        else return z;
+    }
+
+    // Edit Distance based on DP
+    static int editDistanceDP(String str1, String str2, int m, int n)
+    {
+        // Create a table to store results of subproblems
+        int dp[][] = new int[m+1][n+1];
+
+        // Fill d[][] in bottom up manner
+        for (int i=0; i<=m; i++)
+        {
+            for (int j=0; j<=n; j++)
+            {
+                // If first string is empty, only option is to
+                // insert all characters of second string
+                if (i==0)
+                    dp[i][j] = j;  // Min. operations = j
+
+                // If second string is empty, only option is to
+                // remove all characters of second string
+                else if (j==0)
+                    dp[i][j] = i; // Min. operations = i
+
+                // If last characters are same, ignore last char
+                // and recur for remaining string
+                else if (str1.charAt(i-1) == str2.charAt(j-1))
+                    dp[i][j] = dp[i-1][j-1];
+
+                // If the last character is different, consider all
+                // possibilities and find the minimum
+                else
+                    dp[i][j] = 1 + min(dp[i][j-1],  // Insert
+                                       dp[i-1][j],  // Remove
+                                       dp[i-1][j-1]); // Replace
+            }
+        }
+
+        return dp[m][n];
+    }
+
+
+
+    public static void main(String args[])
+    {
+        String str1 = "their";
+        String str2 = "they're";
+        System.out.println( editDistanceDP( str1 , str2 , str1.length(), str2.length()) );
+    }
+}

Dynamic Programming/EditDistance/README.md

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+# Edit Distance Implementation
+
+## Problem Statement
+Given two strings str1 and str2 and below operations that can performed on str1. Find minimum number of edits (operations) required to convert ‘str1’ into ‘str2’. All of the above operations are of equal cost.
+
+## Steps
+1. Create an array to store results of all the subproblems
+2. Check if any of the two strings is empty
+3. If the last characters are same call method recursively
+4. Else-If the last character is different, consider all possibilites and find the minimum