Create 934-shortest-bridge.js

Author: everthis

934-shortest-bridge.js

@@ -0,0 +1,67 @@
+/**
+ * @param {number[][]} A
+ * @return {number}
+ */
+const shortestBridge = function(A) {
+    const h = A.length
+    const w = A[0].length
+    let queue = []
+  
+    let foundOneIsland = false
+    for (let i = 0; i < h && !foundOneIsland; i++) {
+      for (let j = 0; j < w && !foundOneIsland; j++) {
+        if (A[i][j] == 1) {
+          dfs(A, i, j, w, h)
+          foundOneIsland = true
+        }
+      }
+    }
+    // BFS每一个元素向外扩展，直至找到另一个小岛
+    const direction = [0, 1, 0, -1, 0]
+    let result = 0
+    while (queue.length !== 0) {
+      let size = queue.length
+      while (size--) {
+        const item = queue.pop()
+        const x = item.i
+        const y = item.j
+        for (let i = 0; i < 4; i++) {
+          // 向四个方向扩展 技巧
+          const newX = x + direction[i]
+          const newY = y + direction[i + 1]
+          if (newX < 0 || newY < 0 || newX > h - 1 || newY > w - 1 || A[newX][newY] == 2) {
+            continue
+          }
+          // 找到另一个小岛
+          if (A[newX][newY] == 1) {
+            return result
+          }
+          A[newX][newY] = 2
+          queue.unshift({
+            i: newX,
+            j: newY
+          })
+        }
+      }
+      ++result
+    }
+  
+    return result
+  
+    // 通过DFS找到其中一个小岛
+    function dfs (A, i, j, w, h) {
+      if (i < 0 || j < 0 || i > h - 1 || j > w - 1 || A[i][j] != '1') {
+        return
+      }
+  
+      A[i][j] = 2
+      queue.push({
+        i,
+        j
+      })
+      dfs(A, i - 1, j, w, h)
+      dfs(A, i + 1, j, w, h)
+      dfs(A, i, j - 1, w, h)
+      dfs(A, i, j + 1, w, h)
+    }
+  };