Leetcode #1222: Queens That Can Attack the King
In this guide, we solve Leetcode #1222 Queens That Can Attack the King in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
On a 0-indexed 8 x 8 chessboard, there can be multiple black queens and one white king. You are given a 2D integer array queens where queens[i] = [xQueeni, yQueeni] represents the position of the ith black queen on the chessboard.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Array, Matrix, Simulation
Intuition
Grid problems are easiest when you define clear row/column boundaries.
A consistent traversal order prevents off-by-one errors.
Approach
Iterate by rows, columns, or layers depending on the requirement.
Keep bounds updated as the traversal progresses.
Steps:
- Define bounds or directions.
- Visit cells in order.
- Update result and move bounds.
Example
Input: queens = [[0,1],[1,0],[4,0],[0,4],[3,3],[2,4]], king = [0,0]
Output: [[0,1],[1,0],[3,3]]
Explanation: The diagram above shows the three queens that can directly attack the king and the three queens that cannot attack the king (i.e., marked with red dashes).
Python Solution
class Solution:
def queensAttacktheKing(
self, queens: List[List[int]], king: List[int]
) -> List[List[int]]:
n = 8
s = {(i, j) for i, j in queens}
ans = []
for a in range(-1, 2):
for b in range(-1, 2):
if a or b:
x, y = king
while 0 <= x + a < n and 0 <= y + b < n:
x, y = x + a, y + b
if (x, y) in s:
ans.append([x, y])
break
return ans
Complexity
The time complexity is , and the space complexity is . The space complexity is .
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.