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#include "leetcode.h"
class Solution {
public:
int singleNumber(vector<int> &nums) {
int ans;
/*
* unordered_map to track frequency
* unordered_map<key data type, value data type>
* both are int in this case.
*/
unordered_map<int, int> freq;
for (int i = 0; i < nums.size(); i++)
/*
* store frequency
* given 4, 1, 2, 1, 2
* 4 -> once
* 1 -> twice
* 2 -> twice
* output: 4
*/
freq[nums[i]]++;
for (auto i : freq) // traverse map
if (i.second == 1) { // if frequency of any element is 1...
ans = i.first; // that's the answer
break; // exit loop because we have our answer
}
return ans;
}
};
int main() {
vector<int> nums = {4, 1, 2, 1, 2};
Solution obj;
for (int i = 0; i < nums.size(); i++)
cout << nums[i] << ' ';
cout << endl << obj.singleNumber(nums);
}
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