二叉树的广度遍历

src/leecode/No102.java

@@ -0,0 +1,50 @@
+package leecode;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Queue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+/**
+ * 二叉树的广度遍历
+ */
+public class No102 {
+
+    public static void main(String[] args) {
+
+    }
+
+    public static List<List<Integer>> levelOrder(TreeNode root) {
+        List<List<Integer>> result = new ArrayList<>();
+        if (root == null){
+            return result;
+        }
+        Queue<TreeNode> queue = new LinkedBlockingQueue<>();
+        queue.offer(root);
+        while (!queue.isEmpty()) {
+            //当前层数的元素个数
+            int qSize = queue.size();
+            List<Integer> layerList = new ArrayList<>();
+            while (qSize > 0){
+                qSize --;
+                TreeNode node = queue.poll();
+                layerList.add(node.val);
+                if (node.left != null){
+                    queue.offer(node.left);
+                }
+                if (node.right != null){
+                    queue.offer(node.right);
+                }
+            }
+            result.add(layerList);
+        }
+        return result;
+    }
+
+    public static class TreeNode {
+        int val;
+        TreeNode left;
+        TreeNode right;
+        TreeNode(int x) { val = x; }
+    }
+}