leetcode-374-Guess-Number-Higher-or-Lower.md

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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):

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-1 : My number is lower
 1 : My number is higher
 0 : Congrats! You got it!

Examples

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n = 10, I pick 6.

Return 6.

分析

二分法

解决方案1(C++)

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

class Solution {
public:
    int guessNumber(int n) {
        int l = 1, r = n;
        while(l <= r) {
            int mid = l + (r-l) / 2;
            switch(guess(mid)) {
            case 1:
                l = mid + 1;
                break;
            case -1:
                r = mid - 1;
                break;
            default:
                return mid;
            }
        }
        return 1;
    }
};

相关问题

(E) First Bad Version
(M) Guess Number Higher or Lower II

题目来源