输出一个二叉树的宽度

输出一个二叉树的宽度

思路：二叉树的层序遍历（力扣102）的简单变形，记录下每层的节点个数，取最大值即可。

 

二叉树的层序遍历--打印

public static void level(TreeNode root) {

    Queue<TreeNode> queue = new LinkedList<>();
    queue.offer(root);

    while (root != null || !queue.isEmpty()) {
        TreeNode node = queue.poll();
        System.out.println(node.val);
        if (node.left != null) {
            queue.offer(node.left);
        }
        if (node.right != null) {
            queue.offer(node.right);
        }
    }
}

　　

二叉树的层序遍历--带返回值

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public static List<List<Integer>> level2(TreeNode root) {     List<List<Integer>> result = new ArrayList<>();       Queue<TreeNode> queue = new LinkedList<>();     queue.add(root);       while (!queue.isEmpty()) {         int size = queue.size();         List<Integer> level = new ArrayList<>();         for (int i = 0; i < size; i++) {             TreeNode node = queue.poll();             level.add(new Integer(node.val));             if (node.left != null) {                 queue.offer(node.left);             }             if (node.right != null) {                 queue.offer(node.right);             }         }         result.add(level);     }     return result; }

　　

二叉树的层序遍历--最大宽度

 

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public static Integer getWidth(TreeNode root) {         Queue<TreeNode> queue = new LinkedList<>();     queue.add(root);       Integer maxSize = 0;       while (!queue.isEmpty()) {         int size = queue.size();         maxSize = Math.max(maxSize, size);                   for (int i = 0; i < size; i++) {             TreeNode node = queue.poll();             if (node.left != null) {                 queue.offer(node.left);             }             if (node.right != null) {                 queue.offer(node.right);             }         }       }     return maxSize; }