递归数独算法有效但返回错误答案

【问题标题】：Recursive sudoku algorithm works but returns incorrectly递归数独算法有效但返回错误
【发布时间】：2021-06-06 08:31:05
【问题描述】：

对不起下面的代码转储...！

这个算法确实解决了数独难题（作为登录解决 if empty == -1 func），但是一旦所有递归展开，实际输出要么返回原始拼图字符串，要么返回 {error: '难题无法解决'}。

我认为这可能是最终的迭代错误，但我已经重构和重组，直到我脸色发青，无法弄清楚为什么它在展开时没有返回成功的输出。

任何帮助将不胜感激。

  class SudokuSolver {

      validate(puzzleString) {
          //console.log(puzzleString)

          if (puzzleString.length === 0) {
              return {
                  error: 'Required field missing'
              }
          }

          if (puzzleString.length !== 81) {
              return {
                  error: 'Expected puzzle to be 81 characters long'
              }
          }

          if (!/^[0-9.]*$/.test(puzzleString)) {
              return {
                  error: 'Invalid characters in puzzle'
              };
          }

          return true

      }

      createBoard(puzzleString) {
          //create a new row on 0th or 9th iteration
          let puzzleBoard = [
              [],
              [],
              [],
              [],
              [],
              [],
              [],
              [],
              []
          ]
          let puzzle = puzzleString.split('');
          let row = -1

          for (let i = 0; i < puzzle.length; i++) {
              if (i % 9 === 0) {
                  row++
              }

              puzzleBoard[row].push(puzzle[i])

          }
          return puzzleBoard
      }

      checkRowPlacement(board, row, column, value) {

          for (let i = 0; i < 9; i++) {
              if (board[row][i] == value) {
                  return {
                      valid: false,
                      conflict: 'row'
                  }
              }
          }

          return {
              valid: true
          }

      }

      checkColPlacement(board, row, column, value) {

          for (let i = 0; i < 9; i++) {
              if (board[i][column] == value) {
                  return {
                      valid: false,
                      conflict: 'column'
                  };
              }
          }

          return {
              valid: true
          };

      }

      checkRegionPlacement(board, row, column, value) {

          let regionStartRow = parseInt(row / 3) * 3;
          let regionStartCol = parseInt(column / 3) * 3;
          for (let i = regionStartRow; i < regionStartRow + 3; i++) {
              for (let j = regionStartCol; j < regionStartCol + 3; j++) {
                  if (board[i][j] == value) {
                      return {
                          valid: false,
                          conflict: 'region'
                      }
                  }
              }
          }
          return {
              valid: true
          }
      }

      coordToBoard(input) {
          let res = [];
          // A1 -> A = 0, 1 = 0 
          res.push(input.toUpperCase().charCodeAt(0) - 65)
          res.push(parseInt(input.charAt(1)) - 1)


          return res

      }

      checkPlacement(puzzleString, coordinate, value) {
          if (!puzzleString || !coordinate || !value) {
              return {
                  error: 'Required field(s) missing'
              }
          }

          if (this.validate(puzzleString) != true) {
              return this.validate(puzzleString)
          };

          let coordSplit = coordinate.split('')

          if (!/[A-Ia-i]/.test(coordSplit[0] || !/[0-9]/.test(coordSplit[1]))) {
              return {
                  error: 'Invalid coordinate'
              }
          };

          if (value < 1 || value > 9 || isNaN(value)) {
              return {
                  error: 'Invalid value'
              }
          }

          let boardCoords = this.coordToBoard(coordinate)
          //console.log("boardCoords: " + boardCoords)

          let board = this.createBoard(puzzleString)
          //console.log(board)


          let conflicts = []

          if (this.checkRowPlacement(board, boardCoords[0], boardCoords[1], value).valid != true) {
              conflicts.push(this.checkRowPlacement(board, boardCoords[0], boardCoords[1], value).conflict)
          }

          if (this.checkColPlacement(board, boardCoords[0], boardCoords[1], value).valid != true) {
              conflicts.push(this.checkColPlacement(board, boardCoords[0], boardCoords[1], value).conflict)
          }

          if (this.checkRegionPlacement(board, boardCoords[0], boardCoords[1], value).valid != true) {
              conflicts.push(this.checkRegionPlacement(board, boardCoords[0], boardCoords[1], value).conflict)
          }
          //if value is the same as current coordinate make blank and check if valid and if so return true
          if (board[boardCoords[0]][boardCoords[1]] == value) {

              board[boardCoords[0]][boardCoords[1]] = '.'

              if (this.checkRegionPlacement(board, boardCoords[0], boardCoords[1], value).valid == true && this.checkColPlacement(board, boardCoords[0], boardCoords[1], value).valid == true && this.checkRowPlacement(board, boardCoords[0], boardCoords[1], value).valid == true) {

                  return {
                      valid: true
                  }

              }
          }

          if (this.checkRegionPlacement(board, boardCoords[0], boardCoords[1], value).valid != true || this.checkColPlacement(board, boardCoords[0], boardCoords[1], value).valid != true || this.checkRowPlacement(board, boardCoords[0], boardCoords[1], value).valid != true) {
              return {
                  valid: false,
                  conflict: conflicts
              }
          }




          return {
              valid: true
          }

      }

      findUnassignedLocation(puzzleString) {

            return puzzleString.indexOf('.')
          
          
      }

      rowColToCoord(index) {
    
      let col = (index % 9) + 1;
      let row = String.fromCharCode(parseInt(index / 9) + 65)

      
      return row + col
    }


  solve(puzzleString) {
          if (!puzzleString) {
              return {
                  error: 'Required field missing'
              }
          }
          if (this.validate(puzzleString) != true) {
              return this.validate(puzzleString)
          }
          let empty = this.findUnassignedLocation(puzzleString)

          if (empty == -1) {
            console.log('no empties: ' + puzzleString)
              return {solution: puzzleString}
          } else {
            let coord = this.rowColToCoord(empty)

            for (var num = 1; num <= 9; num++) {
                if (this.checkPlacement(puzzleString, coord, num).valid ) {
                    if (!this.solve((puzzleString.substr(0, empty) + num + puzzleString.substr(empty + 1))).error) {
                      console.log('no error: ' + puzzleString)
                      return {solution: puzzleString}
                    }
                    
                }
                
            }
            //console.log('Cannot be solved: ' + puzzleString)
            return {error: 'Puzzle cannot be solved'}
          }
  
  }

          
        
         

  }

  module.exports = SudokuSolver;

这是日志的输出：

Cannot be solved: 7692354188514763.2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
Cannot be solved: 7692354188514769.2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
Cannot be solved: 769235418851476..2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
Cannot be solved: 76923541885147...2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
Cannot be solved: 7692354188514963724321785..1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
Cannot be solved: 76923541885149637243217895617456928339582..6.62.71...9......1945....4.37.4.3..6..
no empties: 769235418851496372432178956174569283395842761628713549283657194516924837947381625
no error: 76923541885149637243217895617456928339584276162871354928365719451692483794738162.
no error: 7692354188514963724321789561745692833958427616287135492836571945169248379473816..
no error: 76923541885149637243217895617456928339584276162871354928365719451692483794738.6..
no error: 7692354188514963724321789561745692833958427616287135492836571945169248379473..6..
no error: 76923541885149637243217895617456928339584276162871354928365719451692483794.3..6..
no error: 769235418851496372432178956174569283395842761628713549283657194516924837.4.3..6..
no error: 769235418851496372432178956174569283395842761628713549283657194516924.37.4.3..6..
no error: 7692354188514963724321789561745692833958427616287135492836571945169.4.37.4.3..6..
no error: 769235418851496372432178956174569283395842761628713549283657194516..4.37.4.3..6..
no error: 76923541885149637243217895617456928339584276162871354928365719451...4.37.4.3..6..
no error: 7692354188514963724321789561745692833958427616287135492836571945....4.37.4.3..6..
no error: 76923541885149637243217895617456928339584276162871354928365.1945....4.37.4.3..6..
no error: 7692354188514963724321789561745692833958427616287135492836..1945....4.37.4.3..6..
no error: 769235418851496372432178956174569283395842761628713549283...1945....4.37.4.3..6..
no error: 76923541885149637243217895617456928339584276162871354928....1945....4.37.4.3..6..
no error: 7692354188514963724321789561745692833958427616287135492.....1945....4.37.4.3..6..
no error: 769235418851496372432178956174569283395842761628713549......1945....4.37.4.3..6..
no error: 7692354188514963724321789561745692833958427616287135.9......1945....4.37.4.3..6..
no error: 769235418851496372432178956174569283395842761628713..9......1945....4.37.4.3..6..
no error: 76923541885149637243217895617456928339584276162871...9......1945....4.37.4.3..6..
no error: 76923541885149637243217895617456928339584276162.71...9......1945....4.37.4.3..6..
no error: 76923541885149637243217895617456928339584276.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496372432178956174569283395842.6.62.71...9......1945....4.37.4.3..6..
no error: 76923541885149637243217895617456928339584..6.62.71...9......1945....4.37.4.3..6..
no error: 7692354188514963724321789561745692833958...6.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496372432178956174569283395....6.62.71...9......1945....4.37.4.3..6..
no error: 76923541885149637243217895617456928339.....6.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496372432178956174569283.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496372432178956174569.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496372432178956174.69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 76923541885149637243217895617..69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 7692354188514963724321789561...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 76923541885149637243217895.1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 7692354188514963724321789..1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496372432178...1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 76923541885149637243217....1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 7692354188514963724321.....1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496372432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 7692354188514963.2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 769235418851496..2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 76923541885149...2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 7692354188514....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 76923541885.4....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 76923541.85.4....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 769235.1.85.4....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 7692.5.1.85.4....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 769..5.1.85.4....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: 7.9..5.1.85.4....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..
no error: ..9..5.1.85.4....2432......1...69.83.9.....6.62.71...9......1945....4.37.4.3..6..

【问题讨论】：

您自己有没有努力解决这个问题？如果是这样，请描述你做了什么。另外，if (this.validate(puzzleString) != true) { return this.validate(puzzleString) } 是怎么回事？真的有必要打两次this.validate(puzzleString)吗？你不能直接return false 吗？
尝试了各种不同的测试和输出放置以尝试阻止它以这种方式展开，关于 this.validate，验证代码根据错误返回特定错误，因此通过调用验证结果返回错误信息

标签： javascript algorithm recursion sudoku

【解决方案1】：

原因是您的代码忽略了可能从递归调用返回的解决方案，而只是返回最初调用它的不完整拼图：

if (!this.solve((puzzleString.substr(0, empty) + num + puzzleString.substr(empty + 1))).error) {
  console.log('no error: ' + puzzleString)
  return {solution: puzzleString} // Wrong. This is not the solution, but the unfinished puzzle.
}

改为这样做：

let result = this.solve((puzzleString.substr(0, empty) + num + puzzleString.substr(empty + 1)));
if (!result.error) {
    console.log('no error: ' + puzzleString)
    return result; // Return what you got from the recursive call (the solution)
}

【讨论】：

太棒了！感谢您清楚地强调该问题，它现在可以正常工作，而且我知道它为什么不工作了。