feat: add weekly contest 410 (#3401)

Author: yanglbme

solution/1000-1099/1035.Uncrossed Lines/README.md

@@ -39,7 +39,7 @@ tags:
 <pre>
 <strong>输入：</strong>nums1 = <span id="example-input-1-1">[1,4,2]</span>, nums2 = <span id="example-input-1-2">[1,2,4]</span>
 <strong>输出：</strong><span id="example-output-1">2</span>
-<strong>解释：</strong>可以画出两条不交叉的线，如上图所示。
+<strong>解释：</strong>可以画出两条不交叉的线，如上图所示。 
 但无法画出第三条不相交的直线，因为从 nums1[1]=4 到 nums2[2]=4 的直线将与从 nums1[2]=2 到 nums2[1]=2 的直线相交。
 </pre>
 

solution/3200-3299/3248.Snake in Matrix/README.md

@@ -0,0 +1,15 @@
+class Solution {
+public:
+    int finalPositionOfSnake(int n, vector<string>& commands) {
+        int x = 0, y = 0;
+        for (const auto& c : commands) {
+            switch (c[0]) {
+            case 'U': x--; break;
+            case 'D': x++; break;
+            case 'L': y--; break;
+            case 'R': y++; break;
+            }
+        }
+        return x * n + y;
+    }
+};

solution/3200-3299/3248.Snake in Matrix/README_EN.md

@@ -0,0 +1,16 @@
+func finalPositionOfSnake(n int, commands []string) int {
+	x, y := 0, 0
+	for _, c := range commands {
+		switch c[0] {
+		case 'U':
+			x--
+		case 'D':
+			x++
+		case 'L':
+			y--
+		case 'R':
+			y++
+		}
+	}
+	return x*n + y
+}

solution/3200-3299/3248.Snake in Matrix/Solution.cpp

@@ -0,0 +1,14 @@
+class Solution {
+    public int finalPositionOfSnake(int n, List<String> commands) {
+        int x = 0, y = 0;
+        for (var c : commands) {
+            switch (c.charAt(0)) {
+                case 'U' -> x--;
+                case 'D' -> x++;
+                case 'L' -> y--;
+                case 'R' -> y++;
+            }
+        }
+        return x * n + y;
+    }
+}

solution/3200-3299/3248.Snake in Matrix/Solution.go

@@ -0,0 +1,14 @@
+class Solution:
+    def finalPositionOfSnake(self, n: int, commands: List[str]) -> int:
+        x = y = 0
+        for c in commands:
+            match c[0]:
+                case "U":
+                    x -= 1
+                case "D":
+                    x += 1
+                case "L":
+                    y -= 1
+                case "R":
+                    y += 1
+        return x * n + y

solution/3200-3299/3248.Snake in Matrix/Solution.java

@@ -0,0 +1,10 @@
+function finalPositionOfSnake(n: number, commands: string[]): number {
+    let [x, y] = [0, 0];
+    for (const c of commands) {
+        c[0] === 'U' && x--;
+        c[0] === 'D' && x++;
+        c[0] === 'L' && y--;
+        c[0] === 'R' && y++;
+    }
+    return x * n + y;
+}

solution/3200-3299/3248.Snake in Matrix/Solution.py

@@ -0,0 +1,274 @@
+---
+comments: true
+difficulty: 中等
+edit_url: https://github.com/doocs/leetcode/edit/main/solution/3200-3299/3249.Count%20the%20Number%20of%20Good%20Nodes/README.md
+---
+
+<!-- problem:start -->
+
+# [3249. 统计好节点的数目](https://leetcode.cn/problems/count-the-number-of-good-nodes)
+
+[English Version](/solution/3200-3299/3249.Count%20the%20Number%20of%20Good%20Nodes/README_EN.md)
+
+## 题目描述
+
+<!-- description:start -->
+
+<p>现有一棵 <strong>无向</strong> 树，树中包含 <code>n</code> 个节点，按从 <code>0</code> 到 <code>n - 1</code> 标记。树的根节点是节点 <code>0</code> 。给你一个长度为 <code>n - 1</code> 的二维整数数组 <code>edges</code>，其中 <code>edges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> 表示树中节点 <code>a<sub>i</sub></code> 与节点 <code>b<sub>i</sub></code> 之间存在一条边。</p>
+
+<p>如果一个节点的所有子节点为根的&nbsp;<span data-keyword="subtree">子树</span>&nbsp;包含的节点数相同，则认为该节点是一个 <strong>好节点</strong>。</p>
+
+<p>返回给定树中<strong> 好节点 </strong>的数量。</p>
+
+<p><strong>子树</strong>&nbsp;指的是一个节点以及它所有后代节点构成的一棵树。</p>
+
+<p>&nbsp;</p>
+
+<p>&nbsp;</p>
+
+<p><strong class="example">示例 1：</strong></p>
+
+<div class="example-block">
+<p><strong>输入：</strong><span class="example-io">edges = [[0,1],[0,2],[1,3],[1,4],[2,5],[2,6]]</span></p>
+
+<p><strong>输出：</strong><span class="example-io">7</span></p>
+
+<p><strong>说明：</strong></p>
+<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/3200-3299/3249.Count%20the%20Number%20of%20Good%20Nodes/images/tree1.png" style="width: 360px; height: 158px;" />
+<p>树的所有节点都是好节点。</p>
+</div>
+
+<p><strong class="example">示例 2：</strong></p>
+
+<div class="example-block">
+<p><strong>输入：</strong><span class="example-io">edges = [[0,1],[1,2],[2,3],[3,4],[0,5],[1,6],[2,7],[3,8]]</span></p>
+
+<p><strong>输出：</strong><span class="example-io">6</span></p>
+
+<p><strong>说明：</strong></p>
+<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/3200-3299/3249.Count%20the%20Number%20of%20Good%20Nodes/images/screenshot-2024-06-03-193552.png" style="width: 360px; height: 303px;" />
+<p>树中有 6 个好节点。上图中已将这些节点着色。</p>
+</div>
+
+<p><strong class="example">示例 3：</strong></p>
+
+<div class="example-block">
+<p><span class="example-io"><b>输入：</b>edges = [[0,1],[1,2],[1,3],[1,4],[0,5],[5,6],[6,7],[7,8],[0,9],[9,10],[9,12],[10,11]]</span></p>
+
+<p><span class="example-io"><b>输出：</b>12</span></p>
+
+<p><strong>解释：</strong></p>
+<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/3200-3299/3249.Count%20the%20Number%20of%20Good%20Nodes/images/rob.jpg" style="width: 450px; height: 277px;" />
+<p>除了节点 9 以外其他所有节点都是好节点。</p>
+</div>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>2 &lt;= n &lt;= 10<sup>5</sup></code></li>
+	<li><code>edges.length == n - 1</code></li>
+	<li><code>edges[i].length == 2</code></li>
+	<li><code>0 &lt;= a<sub>i</sub>, b<sub>i</sub> &lt; n</code></li>
+	<li>输入确保 <code>edges</code> 总表示一棵有效的树。</li>
+</ul>
+
+<!-- description:end -->
+
+## 解法
+
+<!-- solution:start -->
+
+### 方法一：DFS
+
+我们先根据题目给定的边 $\textit{edges}$ 构建出树的邻接表 $\textit{g}$，其中 $\textit{g}[a]$ 表示节点 $a$ 的所有邻居节点。
+
+然后，我们设计一个函数 $\textit{dfs}(a, \textit{fa})$，表示计算以节点 $a$ 为根的子树中的节点数，并累计好节点的数量。其中 $\textit{fa}$ 表示节点 $a$ 的父节点。
+
+函数 $\textit{dfs}(a, \textit{fa})$ 的执行过程如下：
+
+1. 初始化变量 $\textit{pre} = -1$, $\textit{cnt} = 1$, $\textit{ok} = 1$，分别表示节点 $a$ 的某个子树的节点数、节点 $a$ 的所有子树的节点数、以及节点 $a$ 是否为好节点。
+2. 遍历节点 $a$ 的所有邻居节点 $b$，如果 $b$ 不等于 $\textit{fa}$，则递归调用 $\textit{dfs}(b, a)$，返回值为 $\textit{cur}$，并累加到 $\textit{cnt}$ 中。如果 $\textit{pre} < 0$，则将 $\textit{cur}$ 赋值给 $\textit{pre}$；否则，如果 $\textit{pre}$ 不等于 $\textit{cur}$，说明节点 $a$ 的不同子树的节点数不同，将 $\textit{ok}$ 置为 $0$。
+3. 最后，累加 $\textit{ok}$ 到答案中，并返回 $\textit{cnt}$。
+
+在主函数中，我们调用 $\textit{dfs}(0, -1)$，最后返回答案。
+
+时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 表示节点的数量。
+
+<!-- tabs:start -->
+
+#### Python3
+
+```python
+class Solution:
+    def countGoodNodes(self, edges: List[List[int]]) -> int:
+        def dfs(a: int, fa: int) -> int:
+            pre = -1
+            cnt = ok = 1
+            for b in g[a]:
+                if b != fa:
+                    cur = dfs(b, a)
+                    cnt += cur
+                    if pre < 0:
+                        pre = cur
+                    elif pre != cur:
+                        ok = 0
+            nonlocal ans
+            ans += ok
+            return cnt
+
+        g = defaultdict(list)
+        for a, b in edges:
+            g[a].append(b)
+            g[b].append(a)
+        ans = 0
+        dfs(0, -1)
+        return ans
+```
+
+#### Java
+
+```java
+class Solution {
+    private int ans;
+    private List<Integer>[] g;
+
+    public int countGoodNodes(int[][] edges) {
+        int n = edges.length + 1;
+        g = new List[n];
+        Arrays.setAll(g, k -> new ArrayList<>());
+        for (var e : edges) {
+            int a = e[0], b = e[1];
+            g[a].add(b);
+            g[b].add(a);
+        }
+        dfs(0, -1);
+        return ans;
+    }
+
+    private int dfs(int a, int fa) {
+        int pre = -1, cnt = 1, ok = 1;
+        for (int b : g[a]) {
+            if (b != fa) {
+                int cur = dfs(b, a);
+                cnt += cur;
+                if (pre < 0) {
+                    pre = cur;
+                } else if (pre != cur) {
+                    ok = 0;
+                }
+            }
+        }
+        ans += ok;
+        return cnt;
+    }
+}
+```
+
+#### C++
+
+```cpp
+class Solution {
+public:
+    int countGoodNodes(vector<vector<int>>& edges) {
+        int n = edges.size() + 1;
+        vector<int> g[n];
+        for (const auto& e : edges) {
+            int a = e[0], b = e[1];
+            g[a].push_back(b);
+            g[b].push_back(a);
+        }
+        int ans = 0;
+        auto dfs = [&](auto&& dfs, int a, int fa) -> int {
+            int pre = -1, cnt = 1, ok = 1;
+            for (int b : g[a]) {
+                if (b != fa) {
+                    int cur = dfs(dfs, b, a);
+                    cnt += cur;
+                    if (pre < 0) {
+                        pre = cur;
+                    } else if (pre != cur) {
+                        ok = 0;
+                    }
+                }
+            }
+            ans += ok;
+            return cnt;
+        };
+        dfs(dfs, 0, -1);
+        return ans;
+    }
+};
+```
+
+#### Go
+
+```go
+func countGoodNodes(edges [][]int) (ans int) {
+	n := len(edges) + 1
+	g := make([][]int, n)
+	for _, e := range edges {
+		a, b := e[0], e[1]
+		g[a] = append(g[a], b)
+		g[b] = append(g[b], a)
+	}
+	var dfs func(int, int) int
+	dfs = func(a, fa int) int {
+		pre, cnt, ok := -1, 1, 1
+		for _, b := range g[a] {
+			if b != fa {
+				cur := dfs(b, a)
+				cnt += cur
+				if pre < 0 {
+					pre = cur
+				} else if pre != cur {
+					ok = 0
+				}
+			}
+		}
+		ans += ok
+		return cnt
+	}
+	dfs(0, -1)
+	return
+}
+```
+
+#### TypeScript
+
+```ts
+function countGoodNodes(edges: number[][]): number {
+    const n = edges.length + 1;
+    const g: number[][] = Array.from({ length: n }, () => []);
+    for (const [a, b] of edges) {
+        g[a].push(b);
+        g[b].push(a);
+    }
+    let ans = 0;
+    const dfs = (a: number, fa: number): number => {
+        let [pre, cnt, ok] = [-1, 1, 1];
+        for (const b of g[a]) {
+            if (b !== fa) {
+                const cur = dfs(b, a);
+                cnt += cur;
+                if (pre < 0) {
+                    pre = cur;
+                } else if (pre !== cur) {
+                    ok = 0;
+                }
+            }
+        }
+        ans += ok;
+        return cnt;
+    };
+    dfs(0, -1);
+    return ans;
+}
+```
+
+<!-- tabs:end -->
+
+<!-- solution:end -->
+
+<!-- problem:end -->