leetcode解题之374. Guess Number Higher or Lower Java版 (猜数字大小二分查找）

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.

/* 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); *///二分查找猜测数字大小public class Solution extends GuessGame {public int guessNumber(int n) {int start = 1;int end = n;while (start <= end) {// mid = (low + high) / 2;会溢出int mid = start + (end - start) / 2;int res = guess(mid);if (res == 0)return mid;else if (res == 1) {start = mid + 1;} else {end = mid - 1;}}return start;}}