LeetCode-in-Java
374. Guess Number Higher or Lower
Easy
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 - 11 <= pick <= n
Solution
/*
* 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 {
public int guessNumber(int n) {
int start = 0;
int end = n;
while (start <= end) {
int mid = start + (end - start) / 2;
if (guess(mid) == 0) {
return mid;
} else if (guess(mid) == -1) {
end = mid - 1;
} else {
start = mid + 1;
}
}
return -1;
}
// Assume we pick 7
private int guess(int num) {
return Integer.compare(7, num);
}
}