题解 | #蛇形矩阵#

import Foundation

while let line = readLine() {
    
    let n = Int(line)!

    var mat = [[Int]](repeating: [Int](repeating: -1, count: n), count: n)


    var k = 1

    //! 广度优先
    var queue = [(Int,Int)]()

    queue.append((0,0))


 while  !queue.isEmpty {
        
    let count = queue.count
    for _ in 0..<count {
      let tupe = queue.removeFirst()
      
      if (mat[tupe.0][tupe.1] != -1) {
        continue
      }
      
      mat[tupe.0][tupe.1] = k
      k+=1
      //! 第一个元素是 row 第二个元素是 col
      if tupe.0 + tupe.1 + 1 < n {
        queue.append((tupe.0+1,tupe.1))
        queue.append((tupe.0,tupe.1+1))
      }
      
    }
  }

for i in 0..<n {
    var tempArray = [String]()
    for j in 0..<n {
      if (mat[i][j]  != -1) {
        tempArray.append(String(mat[i][j]))
      }
    }
    
    print(tempArray.joined(separator: " "))

  }
  
}

需要注意 矩阵的先后顺序。