🌗 374. 猜数字大小

难度: 🌗

问题描述

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解法

/** 
 * Forward declaration of guess API.
 * @param  num   your guess
 * @return 	     -1 if num is lower than the guess number
 *			      1 if num is higher than the guess number
 *               otherwise return 0
 * int guess(int num);
 */

public class Solution extends GuessGame {
    public int guessNumber(int n) {
        // 思路：
        // 根据题意写出表达式
        return mySol(1, n);
    }

    private int mySol(int low, int high) {
        // 递归终止条件
        if(low == high) {
            return low;
        }
        // 二分，首先判断与中点的大小
        int mid = low + (int)(((long)high - low) >> 1);
        int tmp = guess(mid);
        if(tmp == 0) {
            return mid;
        } else if(tmp < 0) {
            return mySol(low, mid - 1);
        } else {
            return mySol(mid + 1, high);
        }
    }
}

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输出