153. Find Minimum in Rotated Sorted Array
摘要：
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...
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
難度：medium
題目：假設一個按升序排序的陣列在某個未知的軸上旋轉。假定陣列中沒有重複元素。
思路：分情況二叉搜尋
Runtime: 0 ms, faster than 100.00% of Java online submissions for Find Minimum in Rotated Sorted Array.
Memory Usage: 37.6 MB, less than 100.00% of Java online submissions for Find Minimum in Rotated Sorted Array.
class Solution {
public int findMin(int[] nums) {
return findMin(nums, 0, nums.length - 1);
}
public int findMin(int[] nums, int left, int right) {
int mid = left + (right - left) / 2;
// 升序
if (nums[left] <= nums[mid] && nums[mid] <= nums[right]) {
return nums[left];
}
// 降序
if (nums[left] >= nums[mid] && nums[mid] >= nums[right]) {
return nums[right];
}
// 升序佔大降序佔小
if (nums[left] >= nums[mid]) {
return findMin(nums, left, mid);
}
// 升序佔小降序佔大
return findMin(nums, mid, right);
}
}