lintcode(662)Guess Number Game

最新推荐文章于 2025-12-19 15:39:34 发布

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#java #lintcode #简单算法

本文介绍了一种通过二分查找法解决猜数字游戏问题的方法。玩家需猜测由系统选定的一个1到n之间的数字，每次猜测后系统会提示该数字比猜测的数字高还是低。文章详细阐述了使用二分法提高猜测效率的具体实现。

描述：

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):

样例；

n = 10, I pick 4 (but you don't know)

Return 4. Correct !

思路：

采用二分法即可，注意判断是否 n == target => guess(n) == 0 以避免超时。

/* 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 Solution extends GuessGame {
    /**
     * @param n an integer
     * @return the number you guess
     */
    public int guessNumber(int n) {
        // Write your code here
        if(guess(n) == 0){
            return n;
        }
        int low = 1;
        int high = n;
        while(low < high){
            int mid = low + (high - low)/2;
            int record = guess(mid);
            if(record == 0){
                return mid;
            }else if(record == 1){
                low = mid;
            }else if(record == -1){
                high = mid;
            }
        }
        return low;
    }
}