Create 0877-stone-game.cpp

Author: Abe0770

cpp/0877-stone-game.cpp

@@ -0,0 +1,40 @@
+/*
+  Alice and Bob play a game with piles of stones. There are an even number of piles arranged 
+  in a row, and each pile has a positive integer number of stones piles[i].
+
+	The objective of the game is to end with the most stones. The total number of stones across 
+  all the piles is odd, so there are no ties.
+
+	Alice and Bob take turns, with Alice starting first. Each turn, a player takes the entire pile 
+  of stones either from the beginning or from the end of the row. This continues until there are 
+  no more piles left, at which point the person with the most stones wins.
+
+	Assuming Alice and Bob play optimally, return true if Alice wins the game, or false if Bob wins.
+	
+	Ex: Input: piles = [5,3,4,5]
+	Output: true
+	Explanation: 
+	Alice starts first, and can only take the first 5 or the last 5.
+	Say she takes the first 5, so that the row becomes [3, 4, 5].
+	If Bob takes 3, then the board is [4, 5], and Alice takes 5 to win with 10 points.
+	If Bob takes the last 5, then the board is [3, 4], and Alice takes 4 to win with 9 points.
+	This demonstrated that taking the first 5 was a winning move for Alice, so we return true.
+
+  Space: O(n/2)
+  Time : O(1)
+*/
+
+
+class Solution {
+public:
+    bool stoneGame(vector<int>& piles) {
+        int alice = 0, bob = 0, size = piles.size();
+        for(int i = 0 ; i < size/2; i++) {
+            alice = alice + max( piles[i], piles[size - 1- i] );
+            bob = bob + min( piles[i], piles[size - 1- i] );
+        }
+        if(alice > bob)  
+            return true;
+        return false;
+    }
+};