leetcode-463. 岛屿的周长
题目
解法
依题遍历陆地的四个边,如果靠近水,那么算到周长里面,否则不算
<?php class Solution { /** * @param Integer[][] $grid * @return Integer */ function islandPerimeter($grid) { if (empty($grid)) { return 0; } $per = 0; foreach ($grid as $rowKey => $rowGrid) { foreach ($rowGrid as $colKey => $colItem) { if ($colItem != 1) { continue; } $per += intval(!isset($grid[$rowKey - 1][$colKey]) || $grid[$rowKey - 1][$colKey] == 0); $per += intval(!isset($grid[$rowKey][$colKey + 1]) || $grid[$rowKey][$colKey + 1] == 0); $per += intval(!isset($grid[$rowKey + 1][$colKey]) || $grid[$rowKey + 1][$colKey] == 0); $per += intval(!isset($grid[$rowKey][$colKey - 1]) || $grid[$rowKey][$colKey - 1] == 0); } } return $per; } }
还有一种深度遍历的方式
class Solution { /** * @param Integer[][] $grid * @return Integer */ function islandPerimeter($grid) { if (empty($grid)) { return 0; } $per = 0; foreach ($grid as $rowKey => $rowGrid) { foreach ($rowGrid as $colKey => $colItem) { if ($grid[$rowKey][$colKey] == 1) { $per += $this->dfs($grid, $rowKey, $colKey); } } } return $per; } public function dfs(&$grid, $rowKey, $colKey) { if (!isset($grid[$rowKey][$colKey])) { return 0; } if ($grid[$rowKey][$colKey] == 0) { return 0; } if ($grid[$rowKey][$colKey] == 2) { return 0; } $grid[$rowKey][$colKey] = 2; $per = 0; $per += intval(!isset($grid[$rowKey - 1][$colKey]) || $grid[$rowKey - 1][$colKey] == 0); $per += intval(!isset($grid[$rowKey][$colKey + 1]) || $grid[$rowKey][$colKey + 1] == 0); $per += intval(!isset($grid[$rowKey + 1][$colKey]) || $grid[$rowKey + 1][$colKey] == 0); $per += intval(!isset($grid[$rowKey][$colKey - 1]) || $grid[$rowKey][$colKey - 1] == 0); $per += $this->dfs($grid, $rowKey - 1, $colKey); $per += $this->dfs($grid, $rowKey, $colKey + 1); $per += $this->dfs($grid, $rowKey + 1, $colKey); $per += $this->dfs($grid, $rowKey, $colKey - 1); return $per; } }
本文来自博客园,作者:吴丹阳-V,转载请注明原文链接:https://www.cnblogs.com/wudanyang/p/15543960.html
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