Given an array of integers arr
, a lucky integer is an integer which has a frequency in the array equal to its value.
Return a lucky integer in the array. If there are multiple lucky integers return the largest of them. If there is no lucky integer return -1.
Example 1:
Input: arr = [2,2,3,4] Output: 2 Explanation: The only lucky number in the array is 2 because frequency[2] == 2.
Example 2:
Input: arr = [1,2,2,3,3,3] Output: 3 Explanation: 1, 2 and 3 are all lucky numbers, return the largest of them.
Example 3:
Input: arr = [2,2,2,3,3] Output: -1 Explanation: There are no lucky numbers in the array.
Example 4:
Input: arr = [5] Output: -1
Example 5:
Input: arr = [7,7,7,7,7,7,7] Output: 7
Constraints:
1 <= arr.length <= 500
1 <= arr[i] <= 500
A:
class Solution { public: int findLucky(vector<int>& arr) { int lucky = -1; unordered_map<int, int> countMap; for(auto val : arr){ countMap[val] += 1; } vector<int> luckies; auto iter = countMap.begin(); while(iter!= countMap.end()){ if(iter->second == iter->first) luckies.push_back(iter->first); iter++; } if(luckies.size()>0){ lucky = *max_element(luckies.begin(), luckies.end()); } return lucky; } };
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