qiaoxu123
12/3/2018 - 11:37 AM

153. Find Minimum in Rotated Sorted Array

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
test.cpp
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class Solution {
public:
    int findMin(vector<int>& nums) {
        if(nums.size() <= 1)
            return nums[0];
        for(int i = 0;i < nums.size()-1;i++){
            if(nums[i+1] < nums[i])
                return nums[i+1];
        }
        return nums[0];
    }
};
test2.cpp
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//使用二分法进行查找
class Solution {
public:
    int findMin(vector<int>& nums) {
        if(nums.size() <= 1)
            return nums[0];
        int start = 0;
        int end = nums.size() - 1;
        int mid = start;
        
        while(nums[start] >= nums[end]){
            if(end - start == 1){
                mid = end;
                break;
            }
            mid = (start + end)/2;
            if(nums[mid] >= nums[start])
                start = mid;
            else if(nums[mid] <= nums[end])
                end = mid;
        }
        
        return nums[mid];
    }
};
test3.cpp
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//0ms 最优算法

class Solution {
public:
    int findMin(vector<int>& nums) {
        int start=0,end=nums.size()-1;
        
        while (start<end) {
            if (nums[start]<nums[end])
                return nums[start];
            
            int mid = (start+end)/2;
            
            if (nums[mid]>=nums[start]) {
                start = mid+1;
            } else {
                end = mid;
            }
        }
        
        return nums[start];
    }
};