1091. Shortest Path in Binary Matrix

leetcode1091.swift

class Solution {
    func shortestPathBinaryMatrix(_ grid: [[Int]]) -> Int {
        guard !grid.isEmpty, !grid[0].isEmpty else {
            return -1
        }
        
        var visited = grid
        var step = 1
        var queue = [(0,0)]
        if visited[0][0] == 1 {
            return -1
        } else {
            visited[0][0] = 1
        }

        while !queue.isEmpty {
            var nextQueue = [(Int,Int)]()
            
            for point in queue {
                if point == (grid.count-1,grid[0].count-1) {
                    return step
                }
                
                let vectors = [(0,-1),(0,1),(1,-1),(1,1),(1,0),(-1,-1),(-1,1),(-1,0)]
                
                for vector in vectors {
                    let nextPoint = (point.0+vector.0, point.1+vector.1)
                    guard nextPoint.0 >= 0, nextPoint.0 < grid.count, nextPoint.1 >= 0, nextPoint.1 < grid[0].count else {
                        continue
                    }
                    
                    guard visited[nextPoint.0][nextPoint.1] == 0 else {
                        continue
                    }
                    nextQueue.append(nextPoint)
                    visited[nextPoint.0][nextPoint.1] = 1
                }
                
            }
            
            step += 1
            queue = nextQueue
        }
        
        return -1
    }
}