Guess Number Higher or Lower

题目地址：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:

n = 10, I pick 6.Return 6.

很简单，还是二分查找法，反正1到n是有序的：

/** * 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 GuessNumberHigherOrLower {    /*public static int guess(int num) {        if (num > 6)            return 1;        else if (num == 6)            return 0;        else            return -1;    }*/    public static int guessNumber(int n) {        return guessNumberRecur(1, n);    }    public static int guessNumberRecur(int low, int high) {        System.out.println(low + " " + high);        if (low == high)            return low;        int mid = low + (high - low) / 2;        if (guess(mid) == 0)            return mid;        else if (guess(mid) == -1)            return guessNumberRecur(low, mid);        else            return guessNumberRecur(mid + 1, high);    }    public static void main(String[] args) {        System.out.println(guessNumber(100));    }}

时间复杂度为O(logn)。