374. Guess Number Higher or Lower

Problem

We are playing the Guess Game. The game is as follows:
I pick a number from 1 to n. You have to guess which number I picked.
Every time you guess wrong, I'll tell you whether the number is higher or lower.
You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):

-1 : My number is lower
 1 : My number is higher
 0 : Congrats! You got it!

Example

Input: n = 10, pick = 6
Output: 6

Code

// Forward declaration of guess API.
// @param num, your guess
// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
static int var = [](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();

int guess(int num);

class Solution {
public:
    int guessNumber(int n) {
        long left = 1;
        long right = n;
        long mid;
        while(1){
            mid = (left+right)/2;
            cout << mid << endl;
            switch(guess(mid)){
                case -1:
                    right = mid-1;
                    break;
                case 1:
                    left = mid+1;
                    break;
                case 0:
                    return mid;
            }
        }
    }
};

Result

374. Guess Number Higher or Lower.png