Description
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.
Solution
Binary search
最基本的二分写法。
/* 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 left = 1;
int right = n;
while (left <= right) {
int mid = left + (right - left) / 2;
int res = guess(mid);
if (res < 0) {
right = mid - 1;
} else if (res > 0) {
left = mid + 1;
} else {
return mid;
}
}
return -1;
}
}
