75 lines
1.6 KiB
PHP
75 lines
1.6 KiB
PHP
<?php
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/**
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* 8皇后解法，共92种解法 回溯思想
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* Class Queen
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*/
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class Queen
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{
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public $result = [];
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function cal8queens($row)
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{
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if ($row == 8) {
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$this->printQueens();
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return;
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}
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//每一行有8中放法
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for($column = 0; $column < 8; $column++) {
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if ($this->isOk($row, $column)) {
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$this->result[$row] = $column;
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$this->cal8queens($row + 1);
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}
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}
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}
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//row行的column列是否合适
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function isOk($row, $column)
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{
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$leftup = $column - 1;
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$rightdown = $column + 1;
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for ($i = $row - 1; $i >= 0; $i--) {
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//判断上一行的 column 列是否有值
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if ($this->result[$i] == $column) {
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return false;
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}
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//左上角是否有值
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if ($leftup >= 0 && $this->result[$i] == $leftup) {
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return false;
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}
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//右下角是否有值
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if ($rightdown < 8 && $this->result[$i] == $rightdown) {
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return false;
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}
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$leftup--;
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$rightdown++;
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}
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return true;
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}
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//打印
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function printQueens()
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{
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for ($row = 0; $row < 8; $row++) {
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for ($column = 0; $column < 8; $column++) {
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if ($this->result[$row] == $column) {
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echo 'Q';
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} else {
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echo '*';
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}
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}
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echo '<br>';
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}
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}
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}
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$queen = new Queen();
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$queen->cal8queens(0);
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