[Leetcode] First Bad Version

Topics

https://leetcode.com/problems/first-bad-version/

You is 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 was developed based on the previous version and all of the versions after a bad version were 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 T O is bad.

Given an API bool Isbadversion (version) which would return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API. Code

21/21 Test Cases passed
runtime:0 ms

The main need to note is that N may be large, low+high and mid+1 may be more than int, so use long.

Forward Declaration of isbadversion API.
BOOL Isbadversion (int version);

int firstbadversion (int n) {
    if (n = = 1) {
        return 1;
    }
    Long low = 1;
    Long high = n;
    Long mid = 0;
    while (low <= high) {
        mid = (low + high)/2;//may exceed int, so use long
        bool bad = Isbadversion (mid);
        if (bad) {High
            = mid-1,
        } else {Low
            = mid + 1;
        }
    }

    return high + 1;
}

attached: some inputs

Last executed input:2147483647 versions 2147483647 was the first bad
version.

Last executed input:2126753390 versions 1702766719 was the first bad
version.