Create find-winner-on-a-tic-tac-toe-game.cpp

Author: kamyu104

C++/find-winner-on-a-tic-tac-toe-game.cpp

@@ -0,0 +1,25 @@
+// Time:  O(1)
+// Space: O(1)
+
+class Solution {
+public:
+    string tictactoe(vector<vector<int>>& moves) {
+        vector<vector<int>> row(2, vector<int>(3));
+        vector<vector<int>> col(2, vector<int>(3));
+        vector<int> diag(2), anti_diag(2);
+        int p = 0;
+        for (const auto& move : moves) {
+            int r = move[0], c = move[1];
+            ++row[p][r];
+            ++col[p][c];
+            diag[p] += (r == c);
+            anti_diag[p] += (r + c == 2);
+            vector<int> tmp = {row[p][r], col[p][c], diag[p], anti_diag[p]};
+            if (find(tmp.cbegin(), tmp.cend(), 3) != tmp.cend()) {
+                return string(1, "AB"[p]);
+            }
+            p ^= 1;
+        }
+        return  moves.size() == 9 ? "Draw" : "Pending";
+    }
+};