LeetCode 1197. Minimum Knight Moves

Description

https://leetcode.com/problems/minimum-knight-moves/

In an infinite chess board with coordinates from -infinity to +infinity, you have a knight at square [0, 0].

A knight has 8 possible moves it can make, as illustrated below. Each move is two squares in a cardinal direction, then one square in an orthogonal direction.

Return the minimum number of steps needed to move the knight to the square [x, y]. It is guaranteed the answer exists.

Example 1:

Input: x = 2, y = 1
Output: 1
Explanation: [0, 0] → [2, 1]

Example 2:

Input: x = 5, y = 5
Output: 4
Explanation: [0, 0] → [2, 1] → [4, 2] → [3, 4] → [5, 5]

Constraints:

• -300 <= x, y <= 300
• 0 <= |x| + |y| <= 300

Python Solution

Use breadth-first search to how many steps to reach the target position.

class Solution:
    def minKnightMoves(self, x: int, y: int) -> int:
        DIRECTIONS = [
            (-2, -1), (-2, 1), (-1, 2), (1, 2),
            (2, 1), (2, -1), (1, -2), (-1, -2)
            
        ]
        
        queue = deque()
        queue.append((0, 0))
        
        
        distance_dict = {(0, 0): 0}
        
        while queue:
            i, j = queue.popleft()
            
            if (i, j) == (x, y):
                return distance_dict[(i, j)]
            
            for dx, dy in DIRECTIONS:
                next_i, next_j = i + dx, j + dy

                    
                if (next_i, next_j) in distance_dict:
                    continue
                    
                queue.append((next_i, next_j))
                
                distance_dict[(next_i, next_j)] = distance_dict[(i, j)] + 1
                
        return -1