Added day30 and day31 solution

Author: Chirag Shah

…s-of-code-may/kClosestPointsToOrigin.cpp …f-code-may/30.kClosestPointsToOrigin.cpp30-days-of-code-may/kClosestPointsToOrigin.cpp renamed to 30-days-of-code-may/30.kClosestPointsToOrigin.cpp 30-days-of-code-may/kClosestPointsToOrigin.cpp renamed to 30-days-of-code-may/30.kClosestPointsToOrigin.cpp

@@ -0,0 +1,29 @@
+class Solution {
+public:
+    int minDistance(string word1, string word2) {
+        
+        int M = word1.size(), N = word2.size();
+        
+        vector<vector<int>> dp(M + 1, vector<int> (N + 1, 0));
+        
+        for(int i=1; i<=M; i++)
+            dp[i][0] = i;
+        
+        for(int j=1; j<=N; j++)
+            dp[0][j] = j;
+        
+        
+        for(int i=1; i<=M; i++){
+            for(int j=1; j<=N; j++){
+
+                if(word1[i-1] == word2[j-1])
+                    dp[i][j] = dp[i-1][j-1];
+                else{
+                    dp[i][j] = min(dp[i-1][j], min(dp[i][j-1], dp[i-1][j-1])) + 1;
+                }
+                
+            }
+        }
+        return dp[M][N];
+    }
+};