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 3 possible results:
-1: The number I picked is lower than your guess (i.e. pick < num). 1: The number I picked is higher than your guess (i.e. pick > num). 0: The number I picked is equal to your guess (i.e. pick == num). Return the number that I picked.
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 Example 4:
Input: n = 2, pick = 2 Output: 2
Constraints:
1 <= n <= 231 - 1 1 <= pick <= n
/**
* Forward declaration of guess API.
* @param num your guess
* @return -1 if num is lower than the guess number
* 1 if num is higher than the guess number
* otherwise return 0
* int guess(int num);
*/
public class Solution : GuessGame {
public int GuessNumber(int n) {
int low = 1;
int high = n;
while(low<high){
int mid = low + (high-low)/2;
if(guess(mid)>0){
low = mid+1;
}
else if(guess(mid)<0){
high = mid;
}
else{
return mid;
}
}
return low;
}
}Time Complexity: O(logn)
Space Complexity: O(1)
