1700 - 1799
1748 - Sum of Unique Elements (Easy)
Problem Link
https://leetcode.com/problems/sum-of-unique-elements/
Problem Statement
You are given an integer array nums. The unique elements of an array are the elements that appear exactly once in the array.
Return the sum of all the unique elements of nums.
Example 1:
Input: nums = [1,2,3,2]
Output: 4
Explanation: The unique elements are [1,3], and the sum is 4.Example 2:
Input: nums = [1,1,1,1,1]
Output: 0
Explanation: There are no unique elements, and the sum is 0.Example 3:
Input: nums = [1,2,3,4,5]
Output: 15
Explanation: The unique elements are [1,2,3,4,5], and the sum is 15.Constraints:
1 <= nums.length <= 1001 <= nums[i] <= 100
Approach 1: Hash Map
class Solution {
public:
int sumOfUnique(vector<int>& nums) {
unordered_map<int, int> m;
int ans = 0;
// use hash map to count the frequency of each number
for(int x : nums) m[x]++;
// unique number would have frequency of 1
for(auto x : m) {
if(x.second == 1) {
ans += x.first;
}
}
return ans;
}
};1727 - Largest Submatrix With Rearrangements
Find the largest all-ones submatrix after column rearrangements by sorting consecutive column heights within each row.
1751 - Maximum Number of Events That Can Be Attended II
Maximize the value of up to k nonoverlapping events by combining compatible schedules with dynamic programming.
