Solving the eight queens problem by using the Recursive Backtracking Method of javascript

Solving the eight queens problem by using the Recursive Backtracking Method of javascript

The Recursive Backtracking Method of javascript solves the eight queens problem:

I have seen many articles about the eight Queens algorithm on the internet, and I rarely see javascript. Today I will use javascript to solve this problem. If you need it, you can refer to it.

Next I will share with you the solution of the eight queens by the backtracing method, with detailed annotations. There is not much nonsense here.

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Function NQueens (order ){ If (order <4 ){ Console. log ('n' Queens problem apply for order bigger than 3! '); Return; }   Var nQueens = []; Var backTracking = false; RowLoop: For (var row = 0; row <order; row ++ ){ // If row is smaller than 0, the problem is not solved. If (row <0 ){ Console. log ('this N Queens problem has no solution! '); Break; } // The first time a new row is detected If (nQueens [row] === undefined ){ NQueens [row] = []; } // Program block that runs during backtracking For (var col = 0; col <order; col ++ ){ // 0 indicates the location where the queen has been detected and can be placed If (nQueens [row] [col] = 0 ){ Continue; } // In the Backtracking process, if the location can be placed in the Queen's position, it indicates that this location is not verified and needs to be re-processed. Else if (backTracking & nQueens [row] [col] = 1 ){ // You can find that the last row ends at the end of the row, and you need to continue backtracking. If (col = order-1 ){ ResetRow (nQueens, order, row ); Row = row-2; Continue rowLoop; } // The row to be traced has not reached the end of the row. Mark 0 and continue. NQueens [row] [col] = 0; BackTracking = false; Continue; } // Place a queen NQueens [row] [col] = 1; // Locate a location where the queen can be placed and jump out to the next line (only one queen can be placed on one row ). If (isQueenValid (nQueens, row, col )){ Continue rowLoop; } // There should be a queen in each row. No proper position has been found at the end of the column, which indicates that there is a problem with the placement of the Queen in front. You need to trace back! Else if (col = order-1 ){ BackTracking = true; // Both 0 and 1 indicate that this position has been detected. Therefore, we need to clear this line as undefined. ResetRow (nQueens, order, row ); // Subtract 2 because there is an auto-increment at the end of the loop, which is actually returned to the previous row. Row = row-2; // Return to the outer loop and continue Continue rowLoop; } Else { // If the row is not found, continue to detect the row that has not been detected NQueens [row] [col] = 0; Continue; }; } } Return nQueens; } // Clear the row before backtracking Function resetRow (nQueens, order, row ){ For (var col = 0; col <order; col ++ ){ NQueens [row] [col] = undefined; } } // Check whether the location can be placed as queen Function isQueenValid (nQueens, row, col ){ // Row Detection For (var I = 0; I <col; I ++ ){ If (nQueens [row] [I] = 1 ){ Return false; } } For (var j = 1; j <row + 1; j ++ ){ // Column detection: Top left 45 degrees, top right 45 degrees If (nQueens [row-j] [col] = 1 | (nQueens [row-j] [col-j] = 1) | (nQueens [row-j] [col + j] = 1 )){ Return false; } } Return true; }   Function printQ (queens ){ For (var row = 0; row <queens. length; row ++ ){ Var rowText = ''; For (var col = 0; col <queens. length; col ++ ){ If (queens [row] [col] === undefined ){ Queens [row] [col] = 0; } RowText = rowText + queens [row] [col] + ''; } Console. log (rowText ); } }   Var queens = NQueens (8 ); PrintQ (queens );

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