374. 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:

n = 10, I pick 6.Return 6.

这是一个查找问题，首先直接使用for循环查找，会超时，然后采用二分查找。

// Forward declaration of guess API.// @param num, your guess// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0int guess(int num);class Solution {public:    int guessNumber(int n) {        int low = 1;        while(low <= n)        {            int mid = (n + low)/2;            int m = guess(mid);            if(m == 0)            return mid;            else if(m == -1)            n = mid -1;            else            low = mid + 1;        }        //return -1;    }};

提交后发现出现Time Limit Exceeded  2126753390 1702766719

这是因为其中mid的值溢出了，修改之后通过。

// Forward declaration of guess API.// @param num, your guess// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0int guess(int num);class Solution {public:    int guessNumber(int n) {        int low = 1;        while(low <= n)        {            int mid = (n - low)/2 + low;            int m = guess(mid);            if(m == 0)            return mid;            else if(m == -1)            n = mid -1;            else            low = mid + 1;        }        //return -1;    }};