[leetcode]153. Find Minimum in Rotated Sorted Array旋转过有序数组里找最小

Suppose an array sorted in ascending order 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.

Example 1:

Input: [3,4,5,1,2] 
Output: 1

Example 2:

Input: [4,5,6,7,0,1,2]
Output: 0

 

题意：

如题

 

Solution： Binary Search

 

code

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