diff --git a/Index/BFS.md b/Index/BFS.md index 76d30a58..f94d39f5 100644 --- a/Index/BFS.md +++ b/Index/BFS.md @@ -14,6 +14,7 @@ | [821. 字符的最短距离](https://leetcode-cn.com/problems/shortest-distance-to-a-character/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/shortest-distance-to-a-character/solution/by-ac_oier-5bjs/) | 简单 | 🤩🤩🤩🤩 | | [838. 推多米诺](https://leetcode-cn.com/problems/push-dominoes/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/push-dominoes/solution/gong-shui-san-xie-yi-ti-shuang-jie-bfs-y-z52w/) | 中等 | 🤩🤩🤩🤩 | | [938. 二叉搜索树的范围和](https://leetcode-cn.com/problems/range-sum-of-bst/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/range-sum-of-bst/solution/gong-shui-san-xie-yi-ti-shuang-jie-di-gu-q2fo/) | 简单 | 🤩🤩🤩 | +| [965. 单值二叉树](https://leetcode.cn/problems/univalued-binary-tree/) | [LeetCode 题解链接](https://leetcode.cn/problems/univalued-binary-tree/solution/by-ac_oier-zxjl/) | 简单 | 🤩🤩🤩🤩 | | [993. 二叉树的堂兄弟节点](https://leetcode-cn.com/problems/cousins-in-binary-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/cousins-in-binary-tree/solution/gong-shui-san-xie-shu-de-sou-suo-dfs-bfs-b200/) | 简单 | 🤩🤩 | | [1609. 奇偶树](https://leetcode-cn.com/problems/even-odd-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/even-odd-tree/solution/gong-shui-san-xie-yi-ti-shuang-jie-bfs-d-kuyi/) | 中等 | 🤩🤩🤩🤩🤩 | diff --git a/Index/DFS.md b/Index/DFS.md index 304da3f7..8f3398a3 100644 --- a/Index/DFS.md +++ b/Index/DFS.md @@ -32,6 +32,7 @@ | [869. 重新排序得到 2 的幂](https://leetcode-cn.com/problems/reordered-power-of-2/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/reordered-power-of-2/solution/gong-shui-san-xie-yi-ti-shuang-jie-dfs-c-3s1e/) | 中等 | 🤩🤩🤩🤩 | | [872. 叶子相似的树](https://leetcode-cn.com/problems/leaf-similar-trees/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/leaf-similar-trees/solution/gong-shui-san-xie-yi-ti-shuang-jie-di-gu-udfc/) | 简单 | 🤩🤩🤩 | | [938. 二叉搜索树的范围和](https://leetcode-cn.com/problems/range-sum-of-bst/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/range-sum-of-bst/solution/gong-shui-san-xie-yi-ti-shuang-jie-di-gu-q2fo/) | 简单 | 🤩🤩🤩 | +| [965. 单值二叉树](https://leetcode.cn/problems/univalued-binary-tree/) | [LeetCode 题解链接](https://leetcode.cn/problems/univalued-binary-tree/solution/by-ac_oier-zxjl/) | 简单 | 🤩🤩🤩🤩 | | [987. 二叉树的垂序遍历](https://leetcode-cn.com/problems/vertical-order-traversal-of-a-binary-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/vertical-order-traversal-of-a-binary-tree/solution/gong-shui-san-xie-yi-ti-shuang-jie-dfs-h-wfm3/) | 困难 | 🤩🤩🤩🤩🤩 | | [993. 二叉树的堂兄弟节点](https://leetcode-cn.com/problems/cousins-in-binary-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/cousins-in-binary-tree/solution/gong-shui-san-xie-shu-de-sou-suo-dfs-bfs-b200/) | 简单 | 🤩🤩 | | [1239. 串联字符串的最大长度](https://leetcode-cn.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/solution/gong-shui-san-xie-yi-ti-san-jie-jian-zhi-nfeb/) | 中等 | 🤩🤩🤩 | diff --git "a/Index/\344\272\214\345\217\211\346\240\221.md" "b/Index/\344\272\214\345\217\211\346\240\221.md" index fdcf8b05..ecbbcc89 100644 --- "a/Index/\344\272\214\345\217\211\346\240\221.md" +++ "b/Index/\344\272\214\345\217\211\346\240\221.md" @@ -11,6 +11,7 @@ | [783. 二叉搜索树节点最小距离](https://leetcode-cn.com/problems/minimum-distance-between-bst-nodes/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/minimum-distance-between-bst-nodes/solution/gong-shui-san-xie-yi-ti-san-jie-shu-de-s-7r17/) | 简单 | 🤩🤩🤩 | | [863. 二叉树中所有距离为 K 的结点](https://leetcode-cn.com/problems/all-nodes-distance-k-in-binary-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/all-nodes-distance-k-in-binary-tree/solution/gong-shui-san-xie-yi-ti-shuang-jie-jian-x6hak/) | 中等 | 🤩🤩🤩🤩 | | [938. 二叉搜索树的范围和](https://leetcode-cn.com/problems/range-sum-of-bst/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/range-sum-of-bst/solution/gong-shui-san-xie-yi-ti-shuang-jie-di-gu-q2fo/) | 简单 | 🤩🤩🤩 | +| [965. 单值二叉树](https://leetcode.cn/problems/univalued-binary-tree/) | [LeetCode 题解链接](https://leetcode.cn/problems/univalued-binary-tree/solution/by-ac_oier-zxjl/) | 简单 | 🤩🤩🤩🤩🤩 | | [987. 二叉树的垂序遍历](https://leetcode-cn.com/problems/vertical-order-traversal-of-a-binary-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/vertical-order-traversal-of-a-binary-tree/solution/gong-shui-san-xie-yi-ti-shuang-jie-dfs-h-wfm3/) | 困难 | 🤩🤩🤩🤩🤩 | | [993. 二叉树的堂兄弟节点](https://leetcode-cn.com/problems/cousins-in-binary-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/cousins-in-binary-tree/solution/gong-shui-san-xie-shu-de-sou-suo-dfs-bfs-b200/) | 简单 | 🤩🤩 | | [1104. 二叉树寻路](https://leetcode-cn.com/problems/path-in-zigzag-labelled-binary-tree/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/path-in-zigzag-labelled-binary-tree/solution/gong-shui-san-xie-yi-ti-shuang-jie-mo-ni-rw2d/) | 中等 | 🤩🤩🤩 | diff --git "a/LeetCode/461-470/467. \347\216\257\347\273\225\345\255\227\347\254\246\344\270\262\344\270\255\345\224\257\344\270\200\347\232\204\345\255\220\345\255\227\347\254\246\344\270\262\357\274\210\344\270\255\347\255\211\357\274\211.md" "b/LeetCode/461-470/467. \347\216\257\347\273\225\345\255\227\347\254\246\344\270\262\344\270\255\345\224\257\344\270\200\347\232\204\345\255\220\345\255\227\347\254\246\344\270\262\357\274\210\344\270\255\347\255\211\357\274\211.md" index fd759fd6..ac8779c6 100644 --- "a/LeetCode/461-470/467. \347\216\257\347\273\225\345\255\227\347\254\246\344\270\262\344\270\255\345\224\257\344\270\200\347\232\204\345\255\220\345\255\227\347\254\246\344\270\262\357\274\210\344\270\255\347\255\211\357\274\211.md" +++ "b/LeetCode/461-470/467. \347\216\257\347\273\225\345\255\227\347\254\246\344\270\262\344\270\255\345\224\257\344\270\200\347\232\204\345\255\220\345\255\227\347\254\246\344\270\262\357\274\210\344\270\255\347\255\211\357\274\211.md" @@ -1,6 +1,6 @@ ### 题目描述 -这是 LeetCode 上的 **[467. 环绕字符串中唯一的子字符串](https://leetcode.cn/problems/can-i-win/solution/by-ac_oier-0ed9/)** ，难度为 **中等**。 +这是 LeetCode 上的 **[467. 环绕字符串中唯一的子字符串](https://leetcode.cn/problems/unique-substrings-in-wraparound-string/solution/by-ac_oier-qteu/)** ，难度为 **中等**。 Tag : 「线性 DP」、「树状数组」 diff --git "a/LeetCode/961-970/965. \345\215\225\345\200\274\344\272\214\345\217\211\346\240\221\357\274\210\347\256\200\345\215\225\357\274\211.md" "b/LeetCode/961-970/965. \345\215\225\345\200\274\344\272\214\345\217\211\346\240\221\357\274\210\347\256\200\345\215\225\357\274\211.md" new file mode 100644 index 00000000..cc8b9ff9 --- /dev/null +++ "b/LeetCode/961-970/965. \345\215\225\345\200\274\344\272\214\345\217\211\346\240\221\357\274\210\347\256\200\345\215\225\357\274\211.md" @@ -0,0 +1,90 @@ +### 题目描述 + +这是 LeetCode 上的 **[965. 单值二叉树](https://leetcode.cn/problems/univalued-binary-tree/solution/by-ac_oier-zxjl/)** ，难度为 **简单**。 + +Tag : 「DFS」、「BFS」、「二叉树」、「树的遍历」、「层序遍历」 + + + +如果二叉树每个节点都具有相同的值，那么该二叉树就是单值二叉树。 + +只有给定的树是单值二叉树时，才返回 `true`；否则返回 `false`。 + +示例 1： +![](https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/29/screen-shot-2018-12-25-at-50104-pm.png) +``` +输入：[1,1,1,1,1,null,1] + +输出：true +``` +示例 2： +![](https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/29/screen-shot-2018-12-25-at-50050-pm.png) +``` +输入：[2,2,2,5,2] + +输出：false +``` + +提示： +* 给定树的节点数范围是 $[1, 100]￥。 +* 每个节点的值都是整数，范围为 $[0, 99]$ 。 + +--- + +### 递归 + +根据题意进行模拟即可。 + +代码： +```Java +class Solution { + int val = -1; + public boolean isUnivalTree(TreeNode root) { + if (val == -1) val = root.val; + if (root == null) return true; + if (root.val != val) return false; + return isUnivalTree(root.left) && isUnivalTree(root.right); + } +} +``` +* 时间复杂度：$O(n)$ +* 空间复杂度：忽略递归带来的额外空间消耗，复杂度为 $O(1)$ + +--- + +### 迭代 + +也可以使用迭代的方式进行层序遍历。 + +代码： +```Java +class Solution { + public boolean isUnivalTree(TreeNode root) { + int val = root.val; + Deque d = new ArrayDeque<>(); + d.addLast(root); + while (!d.isEmpty()) { + TreeNode poll = d.pollFirst(); + if (poll.val != val) return false; + if (poll.left != null) d.addLast(poll.left); + if (poll.right != null) d.addLast(poll.right); + } + return true; + } +} +``` +* 时间复杂度：$O(n)$ +* 空间复杂度：$O(n)$ + +--- + +### 最后 + +这是我们「刷穿 LeetCode」系列文章的第 `No.965` 篇，系列开始于 2021/01/01，截止于起始日 LeetCode 上共有 1916 道题目，部分是有锁题，我们将先把所有不带锁的题目刷完。 + +在这个系列文章里面，除了讲解解题思路以外，还会尽可能给出最为简洁的代码。如果涉及通解还会相应的代码模板。 + +为了方便各位同学能够电脑上进行调试和提交代码，我建立了相关的仓库：https://github.com/SharingSource/LogicStack-LeetCode 。 + +在仓库地址里，你可以看到系列文章的题解链接、系列文章的相应代码、LeetCode 原题链接和其他优选题解。 +