Chapter 13, Problem 23PE

Program Plan Intro

8 Queens Problem

Program plan:

Filename: “PartialSolution.java”

This code snippet creates a class “PartialSolution”. In the code,

• Define a class “PartialSolution”.
  • Declare the class variables.
  • Define the constructor “PartialSolution”.
    • Define the array “queens”.
  • Define the method “examine()”.
    • Iterate a “for” loop,
      • Iterate the inner “for” loop,
        • If “queens[i]” attacks “queens[j]”.
        • • Return the value of “ABANDON”.
            • If the length of the “queens” is “NQUEENS”,
              • Return the value of “ACCEPT”.
            • Else,
              • Return the value of “CONTINUE”.
  • Define the method “extend()”.
    • Set the value of “result”.
    • Iterate a “for” loop,
      • Get the length of “queens” to “size”.
      • Set the “result[i]”.
      • Iterate a “for” loop,
        • Set “queen[j]” to “result[i]”.
        • • • • • Append the new queen to “ith” column.
            • Return the value of “result”.
  • Define a method “toString()”.
    • Return the queens.
  • Define a method “reflect()”.
    • Define an object “result”.
    • Iterate a “for” loop,
      • Set the value of “result”.
        • • • Return the value.
  • Define a method “rotate()”.
    • Define an object “result”.
    • Iterate a “for” loop,
      • Set the value of “result”.
        • • • Return the value.
  • Define a method “equals()”.
    • Define an object “other”.
    • Create an array list “qs”.
    • Iterate a “for” loop,
      • Add “q” to “qs”.
        • • • Iterate a “for” loop,
              • If the condition is true,
                • Return “false”.
            • Return the value.

Filename: “Queen.java”

This code snippet creates a class “Queen”. In the code,

• Define a class “Queen”.
  • Define the class members “row” and “column”.
  • Define a constructor “Queen()”.
    • Set the value of “row” and “column”.
  • Define the method “attacks()”.
    • Return the result of logical operation.
  • Define a method “toString()”.
    • Return the value.
  • Define a method “rotate()”.
    • Return the value.
  • Define a method “reflect()”.
    • Return the value.
  • Define a method “equals()”.
    • Create the object of “Queen”.
    • Return the value.

Filename: “EightQueens.java”

This code snippet creates a class “EightQueens”. In the code,

• Define a class “EightQueens”.
  • Define array list “sols”.
  • Define the “main” method.
    • Call the method “solve()”.
    • Iterate a “for” loop,
      • Print the elements of “sols”.
  • Define the method “solve()”.
    • Define the variable “exam”.
    • If “exam” equal to “ACCEPT”,
      • Set a variable “reject” equal to “false”.
      • Iterate a “for” loop,
        • Set the value of “reject”.
        • • If the condition is true,
            • Add “sol” to “sols”.
    • If “exam” equal to “ABANDON”,
      • Iterate a “for” loop,
        • Call the method “solve()”.