# 第七十八周ARTS总结
# Algorithm
0ms | 100.00% Run time
39.2MB | 34.28% Memory
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> ans = new ArrayList<>();
if (root == null) {
return ans;
}
// 当前层
List<TreeNode> curLevel = new ArrayList<>();
// 下一层
List<TreeNode> nextLevel = new ArrayList<>();
// 是否从左往右
boolean leftToRight = true;
curLevel.add(root);
while (true) {
if (curLevel.size() == 0) {
break;
}
List<Integer> level = new ArrayList<>();
if (leftToRight) {
for (int i = curLevel.size() - 1; i >= 0; i--) {
TreeNode cur = curLevel.get(i);
level.add(cur.val);
if (cur.left != null) {
nextLevel.add(cur.left);
}
if (cur.right != null) {
nextLevel.add(cur.right);
}
}
} else {
for (int i = curLevel.size() - 1; i >= 0; i--) {
TreeNode cur = curLevel.get(i);
level.add(cur.val);
if (cur.right != null) {
nextLevel.add(cur.right);
}
if (cur.left != null) {
nextLevel.add(cur.left);
}
}
}
ans.add(level);
leftToRight = !leftToRight;
curLevel.clear();
curLevel.addAll(nextLevel);
nextLevel.clear();
}
return ans;
}
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2ms | 14.55% Run time
38.8MB | 78.78% Memory
public int maxDepth(TreeNode root) {
int depth = 0;
if (root == null) {
return depth;
}
List<TreeNode> curLevel = new ArrayList<>();
List<TreeNode> nextLevel = new ArrayList<>();
curLevel.add(root);
while (curLevel.size() != 0) {
depth++;
for (TreeNode treeNode : curLevel) {
if (treeNode.left != null) {
nextLevel.add(treeNode.left);
}
if (treeNode.right != null) {
nextLevel.add(treeNode.right);
}
}
curLevel.clear();
curLevel.addAll(nextLevel);
nextLevel.clear();
}
return depth;
}
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# Review
# Tip
- 可通过
ProcessLifecycleOwner来监听整个APP的生命周期，回到前台、退到后台等 - 可通过设置window的type来让弹窗在其他APP上层
context.startActivity中的context如果不是Activity，需要添加addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)filterIsInstance可以根据类型来过滤集合- kotlin的难点
- 不变性思维
- 空安全思维
- 表达式思维
- 函数思维
- 协程思维
# Share
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