Equivalent Pairs - Amazon Top Interview Questions
Problem Statement :
You are given a list of integers nums. Return the number of pairs i < j such that nums[i] = nums[j]. Constraints 0 ≤ n ≤ 100,000 where n is the length of nums Example 1 Input nums = [3, 2, 3, 2, 2] Output 4 Explanation We have index pairs (0, 2), (1, 3), (1, 4), (3, 4).
Solution :
Solution in C++ :
int solve(vector<int>& nums) {
unordered_map<int, int> m;
int ans = 0;
for (int i = 0; i < nums.size(); i++) {
ans += m[nums[i]]++;
}
return ans;
}
Solution in Java :
import java.util.*;
class Solution {
public int solve(int[] nums) {
Map<Integer, Integer> hm = new HashMap<>();
int r = 0;
for (int i = 0; i < nums.length; i++) {
hm.put(nums[i], hm.getOrDefault(nums[i], 0) + 1);
r = r + hm.get(nums[i]) - 1;
}
return r;
}
}
Solution in Python :
class Solution:
def solve(self, nums):
count = defaultdict(int)
ans = 0
for i in nums:
ans += count[i]
count[i] += 1
return ans
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