374. Guess Number Higher or Lower

#### QUESTION:

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:

``````n = 10, I pick 6.

Return 6.
``````

#### EXPLANATION:

1.第一个坑是：其实第一次的时候是把题目的 guess 反回的值理解反了

2.第二个坑是：int类型的数据可能会溢出

#### SOLUTION:

``````/* The guess API is defined in the parent class GuessGame.
@param num, your guess
@return -1 if my number is lower, 1 if my number is higher, otherwise return 0
int guess(int num); */

public class Solution extends GuessGame {
public int guessNumber(int n) {
int low = 1,high = n;
while (low<high){
int tmp = low+(high-low)/2;
int result = guess(tmp);
if(result == 1)
low = tmp+1;
if (result == -1)
high = tmp;
if(result==0)
return tmp;
}
return low;
}
}
``````
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