Added solution for check if move is legal. (#394)

Author: Xtha-Sunil

C++/check-if-move-is-legal.cpp

@@ -0,0 +1,51 @@
+class Solution {
+public:
+    bool search(vector<vector<char>>& board, int rMove, int cMove, char g_color, int i, int j)
+    {
+        rMove += i;
+        cMove += j;
+        int turn = 1;
+
+
+       // Loop over the path until either condition is certain
+       while(rMove < 8 && cMove < 8 && rMove >= 0 && cMove >= 0
+       && board[rMove][cMove] != '.')
+       {
+        if(turn > 1 && board[rMove][cMove] == g_color) {return true;}
+        else if(board[rMove][cMove] == g_color) return false;
+        turn++;
+        rMove += i;
+        cMove += j;
+       }
+
+       return false;
+    }
+    bool checkMove(vector<vector<char>>& board, int rMove, int cMove, char color) {
+        // A problem about searching the cells around and checking conditions
+        // Eight different moving patterns that needs to be checked
+        // For each pattern we need to ensure that the first next two celles are the
+        // opposite color. After this, we need to find a same color.
+        // If no such exist (either boundary conditions or ".") then return false
+        // OR the results together and return
+        
+        // Early termination:
+        if(board[rMove][cMove] != '.')
+        {
+            return false;
+        }
+        
+
+        // Loop over all possible combinations of row and column traversal
+        for(int i = -1; i <= 1; i++)
+        {
+            for(int j = -1; j <= 1; j++)
+            {
+                if(search(board,  rMove,  cMove, color, i, j))
+                {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+};