**source:**https://leetcode.com/problems/guess-number-higher-or-lower**C/C++**

**Solution to LeetCode**problem

**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 will tell you whether the number I picked is higher or lower than your guess.

You call a pre-defined API `int guess(int num)`

, which returns three possible results:

`-1`

: Your guess is higher than the number I picked (i.e.`num > pick`

).`1`

: Your guess is lower than the number I picked (i.e.`num < pick`

).`0`

: your guess is equal to the number I picked (i.e.`num == pick`

).

Return `the number that I picked`

.

## Examples

**Example 1:**

Input:n = 10, pick = 6

Output:6

**Example 2:**

Input:n = 1, pick = 1

Output:1

**Example 3:**

Input:n = 2, pick = 1

Output:1

## Constraints

`1 <= n <= 2`

^{31}- 1`1 <= pick <= n`

## Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

/**
* 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);
*/
class Solution {
public:
int guessNumber(int n) {
long long l = 0;
long long h = n;
int m, g;
while (l <= h) {
m = (int)((l + h) / 2);
g = guess(m);
if (g == 0)
break;
if (g == -1)
h = m - 1;
if (g == 1)
l = m + 1;
}
return m;
}
};