[leetcode-278]Dungeon Game(java)

最新推荐文章于 2022-07-30 00:36:39 发布

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本文介绍了一种使用二分查找算法来高效确定首次出现故障的产品版本的方法。在一个由多个连续开发的版本组成的序列中，一旦某个版本开始出现故障，之后的所有版本都将受到影响。通过调用一个特殊的API isBadVersion(version)，可以判断指定版本是否为故障版本。本文提供了一个优化的解决方案，以最小化调用该API的次数。

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问题描述：
You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.

Suppose you have n versions [1, 2, …, n] and you want to find out the first bad one, which causes all the following ones to be bad.

You are given an API bool isBadVersion(version) which will return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.

分析：这道题就是采用二分查找的方法，但是要注意，整形溢出
代码如下：236 ms

/* The isBadVersion API is defined in the parent class VersionControl.
      boolean isBadVersion(int version); */

public class Solution extends VersionControl {
    public int firstBadVersion(int n) {
        long begin = 1;
        long end = n;

        while(begin<end){
            long mid = (begin+end)/2;
            if(isBadVersion((int)mid)){
                end = mid-1;
            }else
                begin = mid+1;
        }
        return isBadVersion((int)begin)?(int)begin:(int)begin+1;
    }
}