374. Guess Number Higher or Lower - jiejackyzhang/leetcode-note GitHub Wiki
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.
典型的binary search题目。需要注意的是overflow的处理。
/* 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 = 0;
int high = n;
while(low <= high) {
int mid = low + (high - low) / 2; // avoid overflow
int res = guess(mid);
if(res == 0) {
return mid;
} else if(res == 1) {
low = mid + 1;
} else {
high = mid - 1;
}
}
return n;
}
}