From a1e32680ac4e314969dbf7578caac5b7e80b3aa2 Mon Sep 17 00:00:00 2001
From: jerryfishcode <91447694+jerryfishcode@users.noreply.github.com>
Date: Mon, 27 Sep 2021 16:40:41 +0800
Subject: [PATCH] =?UTF-8?q?=E6=96=B0=E5=A2=9E=20463.=E5=B2=9B=E5=B1=BF?=
 =?UTF-8?q?=E7=9A=84=E5=91=A8=E9=95=BF=20JavaScript=E7=89=88=E6=9C=AC?=
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---
 problems/0463.岛屿的周长.md | 49 ++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/problems/0463.岛屿的周长.md b/problems/0463.岛屿的周长.md
index fd9585d2..e6077456 100644
--- a/problems/0463.岛屿的周长.md
+++ b/problems/0463.岛屿的周长.md
@@ -120,6 +120,55 @@ Python：
 Go：
 
 JavaScript：
+```javascript
+//解法一
+var islandPerimeter = function(grid) {
+    // 上下左右 4 个方向
+    const dirx = [-1, 1, 0, 0], diry = [0, 0, -1, 1];
+    const m = grid.length, n = grid[0].length;
+    let res = 0; //岛屿周长
+    for(let i = 0; i < m; i++){
+        for(let j = 0; j < n; j++){
+            if(grid[i][j] === 1){
+                for(let k = 0; k < 4; k++){ //上下左右四个方向
+                    // 计算周边坐标的x,y
+                    let x = i + dirx[k];
+                    let y = j + diry[k];
+                    // 四个方向扩展的新位置是水域或者越界就会为周长贡献1
+                    if(x < 0  // i在边界上
+                    || x >= m // i在边界上
+                    || y < 0  // j在边界上
+                    || y >= n // j在边界上
+                    || grid[x][y] === 0){ // (x,y)位置是水域
+                        res++;
+                        continue;
+                    }
+                }
+            }
+        }
+    }
+    return res;
+};
+
+//解法二
+var islandPerimeter = function(grid) {
+    let sum = 0; // 陆地数量
+    let cover = 0; // 相邻数量
+    for(let i = 0; i < grid.length; i++){
+        for(let j = 0; j <grid[0].length; j++){
+            if(grid[i][j] === 1){
+                sum++;
+                // 统计上边相邻陆地
+                if(i - 1 >= 0 && grid[i-1][j] === 1) cover++;
+                // 统计左边相邻陆地
+                if(j - 1 >= 0 && grid[i][j-1] === 1) cover++;
+                // 为什么没统计下边和右边？ 因为避免重复计算
+            }
+        }
+    }
+    return sum * 4 - cover * 2;
+};
+```
 
 
 -----------------------