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LeetCode 2978: Symmetric Coordinates Solution

Master LeetCode problem 2978 (Symmetric Coordinates), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2978. Symmetric Coordinates

Medium
Database

Problem Explanation

Explanation:

To solve this problem, we need to find all symmetric pairs of coordinates in a given set of coordinates. Two coordinates (x1, y1) and (x2, y2) are symmetric if x1 = y2 and y1 = x2.

We can solve this problem by iterating through all pairs of coordinates and checking if their symmetric pair exists in the given set of coordinates. We can store the coordinates in a hashmap where the key is the concatenated sum of x and y, and the value is the coordinate itself. Then, for each coordinate, we can check if its symmetric pair exists in the hashmap.

Algorithm:

  1. Create a hashmap to store the coordinates.
  2. Iterate through the given set of coordinates.
  3. For each coordinate (x, y):
    • Calculate the key by summing x and y.
    • Check if the key exists in the hashmap:
      • If it exists, check if the value coordinate's x and y are equal to the current coordinate's y and x respectively.
    • If the symmetric pair is found, add it to the result.
  4. Return the list of symmetric pairs.

Time Complexity: O(n), where n is the number of coordinates. Space Complexity: O(n), to store the coordinates in the hashmap.

:

Solution Code

class Solution {
    public List<List<Integer>> symmetricCoordinates(int[][] coordinates) {
        List<List<Integer>> result = new ArrayList<>();
        Map<Integer, int[]> map = new HashMap<>();
        
        for (int[] coord : coordinates) {
            int key = coord[0] + coord[1];
            if (map.containsKey(key)) {
                int[] symCoord = map.get(key);
                if (symCoord[0] == coord[1] && symCoord[1] == coord[0]) {
                    List<Integer> pair = new ArrayList<>();
                    pair.add(symCoord[0]);
                    pair.add(symCoord[1]);
                    result.add(pair);
                }
            }
            map.put(key, coord);
        }
        
        return result;
    }
}

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