数组类278--第一个错误版本（E）

image.png

AC代码

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

public class Solution extends VersionControl {
    public int firstBadVersion(int n) {
        if(n < 1) {
            return -1;
        }
        int left = 1;
        int right = n;
        int ans = -1;
        while(left <= right) {
            int mid = left + (right - left) / 2;
            if(isBadVersion(mid)) {
                ans = mid;
                right = mid - 1;
            }else {
                left = mid + 1;
            }
        }
        return ans;
    }
}

精髓
跟上一篇类似，简化版本，仅仅去查找左边的端点，换个思路，其实也可以查找右边的端点，都是二分思想