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Program.cs
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Program.cs
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using System;
using System.Collections.Generic;
namespace ShortestPathInBinaryMatrix
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
}
static int ShortestPathBinaryMatrix(int[][] grid)
{
if (grid[0][0] == 1) return -1;
int[] dx = {-1, 1, 0, 0, -1, 1, -1, 1};
int[] dy = {0, 0, -1, 1, -1, -1, 1, 1};
var queue = new Queue<int[]>();
var visited = new HashSet<string>();
queue.Enqueue(new[] {0, 0});
visited.Add("0:0");
var res = 0;
while (queue.Count != 0)
{
var count = queue.Count;
res++;
for (int i = 0; i < count; i++)
{
var cur = queue.Dequeue();
if (cur[0] == grid.Length - 1 && cur[1] == grid[0].Length - 1)
return res;
for (int j = 0; j < 8; j++)
{
int newX = cur[0] + dx[j];
int newY = cur[1] + dy[j];
if (newX < 0 || newX >= grid.Length || newY < 0 || newY >= grid[0].Length)
continue;
if (grid[newX][newY] == 0 && visited.Add($"{newX}:{newY}"))
queue.Enqueue(new[] {newX, newY});
}
}
}
return -1;
}
public int ShortestPathBinaryMatrix_DP(int[][] grid)
{
if (grid[0][0] == 1 || grid[^1][^1] == 1) return -1;
int n = grid.Length;
var dp = new int[n][];
for (int i = 0; i < n; i++)
{
dp[i] = new int[n];
Array.Fill(dp[i], int.MaxValue);
}
var queue = new Queue<int[]>();
queue.Enqueue(new int[] { 0, 0, 1 });
dp[0][0] = 1;
int[] dx = { -1, 1, 0, 0, -1, 1, -1, 1 };
int[] dy = { 0, 0, -1, 1, -1, -1, 1, 1 };
while (queue.Count != 0)
{
var cur = queue.Dequeue();
if (cur[0] == n - 1 && cur[1] == n - 1)
return cur[2];
for (int i = 0; i < 8; i++)
{
int newX = cur[0] + dx[i], newY = cur[1] + dy[i];
if (newX < 0 || newX >= n || newY < 0 || newY >= n || grid[newX][newY] == 1)
continue;
if (dp[newX][newY] <= cur[2] + 1)
continue;
dp[newX][newY] = cur[2] + 1;
queue.Enqueue(new int[] { newX, newY, cur[2] + 1 });
}
}
return -1;
}
}
}