[leetcode]Array-697. Degree of an Array

Posted 2020-10-20 chenhan05

Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements.

Your task is to find the smallest possible length of a (contiguous) subarray of nums, that has the same degree as nums.

Example 1:

Input: [1, 2, 2, 3, 1]
Output: 2
Explanation: 
The input array has a degree of 2 because both elements 1 and 2 appear twice.
Of the subarrays that have the same degree:
[1, 2, 2, 3, 1], [1, 2, 2, 3], [2, 2, 3, 1], [1, 2, 2], [2, 2, 3], [2, 2]
The shortest length is 2. So return 2.

 

Example 2:

Input: [1,2,2,3,1,4,2]
Output: 6

class Solution {  
 2 public:  
 3     int findShortestSubArray(vector<int>& nums) {  
 4         int len = nums.size() ;  
 5         if (len < 2)  
 6             return len ;  
 7         int Max = 0 ;  
 8         unordered_map<int,int> startIndex , count ;  
 9         int res = len ;  
10         for(int i = 0 ; i < len ; i++){  
11             if (startIndex.count(nums[i]) == 0)  
12                 startIndex[nums[i]] = i ;  
13             count[nums[i]]++ ;  
14             if (count[nums[i]] > Max){  
15                 res = i - startIndex[nums[i]] + 1 ;  
16                 Max = count[nums[i]] ;  
17             }  
18             if (count[nums[i]] == Max){  
19                 res = min(i - startIndex[nums[i]] + 1 , res) ;    
20             }  
21         }  
22         return res ;  
23     }  
24 };