Find Minimum in Rotated Sorted Array leetcode

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).

Find the minimum element.

You may assume no duplicate exists in the array.

case1: mid > end 所以往mid右边找最小值
case2: mid < start mid左边找最小值
算法的时间复杂度变成O(n)

public class Solution {

    public int findMin(int[] num) {
        if (num == null || num.length == 0) {
            return -1;
        }
        int start = 0;
        int end = num.length - 1;
        int mid;
        while (start + 1 < end) {
            mid = (start + end) / 2;
            if (num[mid] >= num[end]) {//case 1
                start = mid;
            } else {//case 2
                end = mid;
            }
        }
        if (num[start] < num[end]) {
            return num[start];
        } else {
            return num[end];
        }
    }
}