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• 845. 八数码
• • 题意
  • 思路
  • 代码

845. 八数码

• 题意

• 思路

  注意:

  • 通过字符串来记录每一次的状态
  • 这样获取某一个元素的二维坐标, n代表行数, m代表列数
    • x = id // n
    • y = id % m

• 代码

  '''
  Author: NEFU AB-IN
  Date: 2022-03-02 16:49:23
  FilePath: \ACM\Acwing\845.py
  LastEditTime: 2022-03-02 17:20:48
  '''
  
  from collections import Counter, deque
  
  d = Counter()
  
  
  def bfs(start):
      q = deque()
      q.appendleft(start)
      end = '12345678x'
      while q:
          t = q.pop()
          if t == end:
              return d[t]
          dx = [-1, 0, 1, 0]
          dy = [0, 1, 0, -1]
  
          id = t.index('x')
          x, y = id // 3, id % 3
          for i in range(4):
              x1 = x + dx[i]
              y1 = y + dy[i]
              tmp = list(t)
              if x1 >= 0 and x1 < 3 and y1 >= 0 and y1 < 3:
                  tmp[id], tmp[x1 * 3 + y1] = tmp[x1 * 3 + y1], tmp[id]
                  tmp = "".join(tmp)
                  if not d[tmp]:
                      q.appendleft(tmp)
                      d[tmp] = d[t] + 1
      return -1
  
  
  start = "".join(input().split())
  print(bfs(start))