[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

 1 class Solution {
 2      public int findMin(int[] num) {
 3         if (num == null || num.length == 0) {
 4             return 0;
 5         }
 6         if (num.length == 1) {
 7             return num[0];
 8         }
 9         int start = 0, end = num.length - 1;
10         while (start < end) {
11             int mid = (start + end) / 2;
12             if (mid > 0 && num[mid] < num[mid - 1]) {
13                 return num[mid];
14             }
15             if (num[start] <= num[mid] && num[mid] > num[end]) {
16                 start = mid + 1;
17             } else {
18                 end = mid - 1;
19             }
20         }
21         return num[start];
22     }
23 }