LeetCode Find Minimum in Rotated Sorted Array

1.题目

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.

2.解决方案

class Solution {
public:
    int findMin(vector<int> &num) {
        if(num[0] <= num[num.size() - 1]){
            return num[0];
        }

        int leftIndex = 0;
        int rightIndex = num.size() - 1;

        while((leftIndex + 1) < rightIndex){
            int midIndex = (leftIndex + rightIndex) / 2;
            if(num[midIndex] < num[leftIndex]){
                rightIndex = midIndex;
            }else{
                leftIndex = midIndex;
            }
        }
         return min(num[leftIndex], num[rightIndex]);

    }
};

思路：如果是N的时间复杂度肯定太慢了。可以用二分查找。这个跟二分查找的不同之处是，while里面的判断方式，这样可以留下两个数。因为我们也不知道究竟谁比较小。所以最后还要再找到最小的值。

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