【leetcode】猜数字大小

int guessNumber(int n){

    int num = 1+(n-1)/2;
    int left=1,right=n;
    while(1)
    {
        int ret = guess(num);
        if(ret == 1)
            left=num+1;
        else if(ret == -1)
            right=num-1;
        else
            return num;
        num = left+ (right-left)/2;
    }
}