Find Minimum in Rotated Sorted Array

Find Minimum in Rotated Sorted Array

问题：

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.

思路：

　　变形后的二分查找

我的代码：

public class Solution {

 public int findMin(int[] num) {

        if(num == null || num.length == 0) return -1;

        int left = 0;

        int right = num.length - 1;

        while(left + 1 < right)

        {

            int mid = (left + right)/2;

            int leftVal = num[left];

            int rightVal = num[right];

            int midVal = num[mid];

            if(leftVal <= midVal && midVal < rightVal)   return num[left];

            else if(midVal > rightVal)  left = mid;

            else right = mid;

        }

        if(num[left] <= num[right]) return num[left];

        else return num[right];

    }

}

View Code

学习之处；

　　此种方法是改种后的二分查找，常规二分查找 left <= right left = mid - 1 or right = mid + 1,而此时变形为left = mid, right = mid,这样的话，如果判断条件还是left<=right，则无法跳出循环了，所以只能是left + 1 < right