LeetCode 3015: Count the Number of Houses at a Certain Distance I Solution

Master LeetCode problem 3015 (Count the Number of Houses at a Certain Distance I), 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.

3015. Count the Number of Houses at a Certain Distance I

Medium

Breadth-First Search Graph Prefix Sum

Problem Explanation

Explanation

To solve this problem, we can iterate through all possible pairs of houses and calculate the minimum number of streets needed to travel between them. For each pair, we calculate the distance using the street connecting houses x and y, and then determine the minimum number of streets required to reach one house from the other. We maintain a count of pairs for each distance k.

Iterate through all pairs of houses.
Calculate the distance between the houses using the street connecting x and y.
Determine the minimum streets required to reach one house from the other.
Update the count of pairs for each distance k.
Return the counts as the result array.

Time Complexity: O(n^2) where n is the number of houses. Space Complexity: O(n) for the result array.

Solution Code

class Solution {
    public int[] countPairs(int n, int x, int y) {
        int[] result = new int[n];
        
        for (int i = 1; i <= n; i++) {
            for (int j = i + 1; j <= n; j++) {
                int distance = Math.min(Math.abs(x - i) + Math.abs(y - j) + 1, Math.abs(y - i) + Math.abs(x - j) + 1);
                result[distance - 1]++;
            }
        }
        
        return result;
    }
}

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