[374] Guess Number Higher or Lower

雖然一開始也是有點看不懂，但沒想到最後是個歡樂的題目？！

倒是，到底 l 應不應該直接就變成  mid+1 呢 XD?!

/**

* Forward declaration of guess API.

* @param num your guess

* @return -1 if num is higher than the picked number

* 1 if num is lower than the picked number

* otherwise return 0

* int guess(int num);

*/

int guessNumber(int n){

int l=1;

int r=n;

while (l<r)

{

int mid = l+(r-l)/2;

int ans = guess(mid);

if (ans == 0)

return mid;

else if (ans > 0)

// l= (l==mid)? (mid+1):mid;

l=mid+1;

else

r=mid;

}

return l;

}