【一天一道LeetCode】#374. Guess Number Higher or Lower

一天一道LeetCode

（一）题目

（二）解题

// 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 i = 0;
int j = n;
//二分查找法
while(i<=j)
{
int mid = i+(j-i)/2;//取中点
int flag = guess(mid);//返回大于、小于或等于
if(flag == 0) return mid;
else if(flag == -1) j = mid-1;
else i = mid+1;
}
return 0;
}
};