https://leetcode.com/problems/guess-number-higher-or-lower/
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 :
Input: n = 10, pick = 6
Output: 6
题解：二分法
代码：
// Forward declaration of guess API.
// @param num, your guess
// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
int guess(int num);
class Solution {
public:
int guessNumber(int n) {
int left = 1;
int right = n;
int mid;
while(left <= right) {
mid = (right - left) / 2 + left;
if(guess(mid) == 0) return mid;
else if(guess(mid) == 1) left = mid + 1;
else right = mid - 1;
}
return mid;
}
};