[LintCode] 611. Knight Shortest Path
作者:互联网
Given a knight in a chessboard (a binary matrix with 0
as empty and 1
as barrier) with a source
position, find the shortest path to a destination
position, return the length of the route.
Return -1
if destination cannot be reached.
Example
Example 1:
Input:
[[0,0,0],
[0,0,0],
[0,0,0]]
source = [2, 0] destination = [2, 2]
Output: 2
Explanation:
[2,0]->[0,1]->[2,2]
Example 2:
Input:
[[0,1,0],
[0,0,1],
[0,0,0]]
source = [2, 0] destination = [2, 2]
Output:-1
Clarification
If the knight is at (x, y), he can get to the following positions in one step:
(x + 1, y + 2)
(x + 1, y - 2)
(x - 1, y + 2)
(x - 1, y - 2)
(x + 2, y + 1)
(x + 2, y - 1)
(x - 2, y + 1)
(x - 2, y - 1)
Notice
source and destination must be empty.
Knight can not enter the barrier.
Path length refers to the number of steps the knight takes.
/** * Definition for a point. * class Point { * int x; * int y; * Point() { x = 0; y = 0; } * Point(int a, int b) { x = a; y = b; } * } */ public class Solution { /** * @param grid: a chessboard included 0 (false) and 1 (true) * @param source: a point * @param destination: a point * @return: the shortest path */ int row = 0; int col = 0; public int shortestPath(boolean[][] grid, Point source, Point destination) { // write your code here row = grid.length; col = grid[0].length; Queue<Point> queue = new LinkedList<>(); int step = 0; int[][] directions = new int[][]{{1, 2}, {1, -2}, {-1, 2}, {-1, -2}, {2, 1}, {2, -1}, {-2, 1}, {-2, -1}}; queue.offer(source); grid[source.x][source.y] = true; while (!queue.isEmpty()) { int size = queue.size(); for(int i = 0; i < size; i++) { Point cur = queue.poll(); if (cur.x == destination.x && cur.y == destination.y) { return step; } for (int[] dir: directions) { int newX = dir[0] + cur.x; int newY = dir[1] + cur.y; Point newP = new Point(newX, newY); if (isValid(newP, grid)) { queue.offer(newP); grid[newX][newY] = true; } } } step += 1; } return -1; } private boolean isValid(Point p, boolean[][] visited) { if (p.x < 0 || p.x >= row || p.y < 0 || p.y >= col || visited[p.x][p.y]) { return false; } return true; } }
标签:611,return,Point,int,Knight,destination,LintCode,source,grid 来源: https://www.cnblogs.com/xuanlu/p/12530765.html