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NoOfGoodPairs.cpp
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61 lines (49 loc) · 1 KB
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/*
Given an array of integers nums, return the number of good pairs.
A pair (i, j) is called good if nums[i] == nums[j] and i < j.
Example 1:
Input: nums = [1,2,3,1,1,3]
Output: 4
Explanation: There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed.
Example 2:
Input: nums = [1,1,1,1]
Output: 6
Explanation: Each pair in the array are good.
Example 3:
Input: nums = [1,2,3]
Output: 0
*/
#include<bits/stdc++.h>
using namespace std;
//Naive solution
class Solution {
public:
int numIdenticalPairs(vector<int>& nums) {
int n=nums.size();
int cnt=0;
for(int i=0;i<n-1;i++)
{
for(int j=i+1;j<n;j++)
{
if(nums[i]==nums[j])
cnt++;
}
}
return cnt;
}
};
//Optimized solution with extra space
class Solution {
public:
int numIdenticalPairs(vector<int>& nums) {
int n=nums.size();
int sum=0;
int mem[1000]={0};
for(int i=0;i<n;i++)
{
sum+=mem[nums[i]];
++mem[nums[i]];
}
return sum;
}
};