Update sum-game.cpp

Author: kamyu104

C++/sum-game.cpp

@@ -5,8 +5,8 @@ class Solution {
 public:
     bool sumGame(string num) {
         // (1) if both halfs have '?',
-        //     alice will try to choose a number from one half to maximize or minimize the diff of both half sums,
-        //     and bob will try to choose the same number frome the other half to minimize or maximize the diff of both half sums.
+        //     alice will optimally choose 9 or 0 from one half to maximize or minimize the diff of both half sums,
+        //     and bob will optimally choose the same number from the other half to minimize or maximize the diff of both half sums.
         //     in the end, it turns that only one half has '?' and the diff of both half sums is still the same as original
         // (2) if smaller half has no '?', then alice wins
         // (3) if smaller half has '?'