Merge pull request #2677 from nineninee/km0104

添加 卡码网0104.建造最大岛屿 JS版

Author: youngyangyang04

problems/kamacoder/0104.建造最大岛屿.md

@@ -532,6 +532,123 @@ if __name__ == "__main__":
 
 ### Javascript
 
+```javascript
+const r1 = require('readline').createInterface({ input: process.stdin });
+// 创建readline接口
+let iter = r1[Symbol.asyncIterator]();
+// 创建异步迭代器
+const readline = async () => (await iter.next()).value;
+
+let graph // 地图
+let N, M // 地图大小
+let visited // 访问过的节点, 标记岛屿
+const dir = [[0, 1], [1, 0], [0, -1], [-1, 0]] //方向
+
+let count = 0 // 统计岛屿面积
+let areaMap = new Map() // 存储岛屿面积
+
+
+// 读取输入，初始化地图
+const initGraph = async () => {
+  let line = await readline();
+  [N, M] = line.split(' ').map(Number);
+  graph = new Array(N).fill(0).map(() => new Array(M).fill(0))
+  visited = new Array(N).fill(0).map(() => new Array(M).fill(0))
+
+  for (let i = 0; i < N; i++) {
+    line = await readline()
+    line = line.split(' ').map(Number)
+    for (let j = 0; j < M; j++) {
+      graph[i][j] = line[j]
+    }
+  }
+}
+
+/**
+ * @description: 从（x，y）开始深度优先遍历地图
+ * @param {*} graph 地图
+ * @param {*} visited 可访问节点
+ * @param {*} x 开始搜索节点的下标
+ * @param {*} y 开始搜索节点的下标
+ * @param {*} mark 当前岛屿的标记
+ * @return {*}
+ */
+const dfs = (graph, visited, x, y, mark) => {
+  if (visited[x][y] != 0) return
+  visited[x][y] = mark
+  count++
+
+  for (let i = 0; i < 4; i++) {
+    let nextx = x + dir[i][0]
+    let nexty = y + dir[i][1]
+    if (nextx < 0 || nextx >= N || nexty < 0 || nexty >= M) continue //越界, 跳过
+
+    // 已访问过, 或者是海洋, 跳过
+    if (visited[nextx][nexty] != 0 || graph[nextx][nexty] == 0) continue
+
+    dfs(graph, visited, nextx, nexty, mark)
+  }
+}
+
+(async function () {
+
+  // 读取输入，初始化地图
+  await initGraph()
+
+  let isAllLand = true //标记整个地图都是陆地
+
+  let mark = 2 // 标记岛屿
+  for (let i = 0; i < N; i++) {
+    for (let j = 0; j < M; j++) {
+      if (graph[i][j] == 0 && isAllLand) isAllLand = false
+      if (graph[i][j] === 1 && visited[i][j] === 0) {
+        count = 0
+        dfs(graph, visited, i, j, mark)
+        areaMap.set(mark, count)
+        mark++
+      }
+    }
+  }
+
+  // 如果全是陆地, 直接返回面积
+  if (isAllLand) {
+    console.log(N * M);
+    return
+  }
+
+  let result = 0  // 记录最后结果
+  let visitedIsland = new Map() //标记访问过的岛屿, 因为海洋四周可能是同一个岛屿, 需要标记避免重复统计面积
+  for (let i = 0; i < N; i++) {
+    for (let j = 0; j < M; j++) {
+      if (visited[i][j] === 0) {
+        count = 1  // 记录连接之后的岛屿数量
+        visitedIsland.clear()  // 每次使用时，清空
+
+        // 计算海洋周围岛屿面积
+        for (let m = 0; m < 4; m++) {
+          const nextx = i + dir[m][0]
+          const nexty = j + dir[m][1]
+          if (nextx < 0 || nextx >= N || nexty < 0 || nexty >= M) continue //越界, 跳过
+
+          const island = visited[nextx][nexty]
+          if (island == 0 || visitedIsland.get(island)) continue// 四周是海洋或者访问过的陆地 跳过
+
+          // 标记为访问, 计算面积
+          visitedIsland.set(island, true)
+          count += areaMap.get(visited[nextx][nexty])
+        }
+
+        result = Math.max(result, count)
+      }
+    }
+  }
+
+  console.log(result);
+})()
+```
+
+
+
 ### TypeScript
 
 ### PhP