1971.寻找图中是否存在路径:解决栈溢出问题

.obsidian/app.json

@@ -0,0 +1 @@
+{}

.obsidian/appearance.json

@@ -0,0 +1,3 @@
+{
+ "accentColor": ""
+}

.obsidian/core-plugins-migration.json

@@ -0,0 +1,30 @@
+{
+ "file-explorer": true,
+ "global-search": true,
+ "switcher": true,
+ "graph": true,
+ "backlink": true,
+ "canvas": true,
+ "outgoing-link": true,
+ "tag-pane": true,
+ "properties": false,
+ "page-preview": true,
+ "daily-notes": true,
+ "templates": true,
+ "note-composer": true,
+ "command-palette": true,
+ "slash-command": false,
+ "editor-status": true,
+ "bookmarks": true,
+ "markdown-importer": false,
+ "zk-prefixer": false,
+ "random-note": false,
+ "outline": true,
+ "word-count": true,
+ "slides": false,
+ "audio-recorder": false,
+ "workspaces": false,
+ "file-recovery": true,
+ "publish": false,
+ "sync": false
+}

.obsidian/core-plugins.json

@@ -0,0 +1,20 @@
+[
+ "file-explorer",
+ "global-search",
+ "switcher",
+ "graph",
+ "backlink",
+ "canvas",
+ "outgoing-link",
+ "tag-pane",
+ "page-preview",
+ "daily-notes",
+ "templates",
+ "note-composer",
+ "command-palette",
+ "editor-status",
+ "bookmarks",
+ "outline",
+ "word-count",
+ "file-recovery"
+]

.obsidian/workspace.json

@@ -0,0 +1,147 @@
+{
+ "main": {
+ "id": "14608cf8b641f651",
+ "type": "split",
+ "children": [
+ {
+ "id": "7b559c19d2418ebd",
+ "type": "tabs",
+ "children": [
+ {
+ "id": "a006865600bc4e20",
+ "type": "leaf",
+ "state": {
+ "type": "empty",
+ "state": {}
+ }
+ }
+ ]
+ }
+ ],
+ "direction": "vertical"
+ },
+ "left": {
+ "id": "340e6a79c670a47b",
+ "type": "split",
+ "children": [
+ {
+ "id": "c5f81ca398c18cda",
+ "type": "tabs",
+ "children": [
+ {
+ "id": "51f9f8f44ecceb89",
+ "type": "leaf",
+ "state": {
+ "type": "file-explorer",
+ "state": {
+ "sortOrder": "alphabetical"
+ }
+ }
+ },
+ {
+ "id": "0cff567244d7cff5",
+ "type": "leaf",
+ "state": {
+ "type": "search",
+ "state": {
+ "query": "1971",
+ "matchingCase": false,
+ "explainSearch": false,
+ "collapseAll": false,
+ "extraContext": false,
+ "sortOrder": "alphabetical"
+ }
+ }
+ },
+ {
+ "id": "209574c920774a4d",
+ "type": "leaf",
+ "state": {
+ "type": "bookmarks",
+ "state": {}
+ }
+ }
+ ],
+ "currentTab": 1
+ }
+ ],
+ "direction": "horizontal",
+ "width": 300
+ },
+ "right": {
+ "id": "93ce8f4c11893983",
+ "type": "split",
+ "children": [
+ {
+ "id": "da8cbb56e5ee7c52",
+ "type": "tabs",
+ "children": [
+ {
+ "id": "dfccbc1ebc0bb831",
+ "type": "leaf",
+ "state": {
+ "type": "backlink",
+ "state": {
+ "collapseAll": false,
+ "extraContext": false,
+ "sortOrder": "alphabetical",
+ "showSearch": false,
+ "searchQuery": "",
+ "backlinkCollapsed": false,
+ "unlinkedCollapsed": true
+ }
+ }
+ },
+ {
+ "id": "9d2201419a111fe4",
+ "type": "leaf",
+ "state": {
+ "type": "outgoing-link",
+ "state": {
+ "linksCollapsed": false,
+ "unlinkedCollapsed": true
+ }
+ }
+ },
+ {
+ "id": "dc86ccf1b01bc02c",
+ "type": "leaf",
+ "state": {
+ "type": "tag",
+ "state": {
+ "sortOrder": "frequency",
+ "useHierarchy": true
+ }
+ }
+ },
+ {
+ "id": "ec512545d2a7f2e5",
+ "type": "leaf",
+ "state": {
+ "type": "outline",
+ "state": {}
+ }
+ }
+ ]
+ }
+ ],
+ "direction": "horizontal",
+ "width": 300,
+ "collapsed": true
+ },
+ "left-ribbon": {
+ "hiddenItems": {
+ "switcher:打开快速切换": false,
+ "graph:查看关系图谱": false,
+ "canvas:新建白板": false,
+ "daily-notes:打开/创建今天的日记": false,
+ "templates:插入模板": false,
+ "command-palette:打开命令面板": false
+ }
+ },
+ "active": "a006865600bc4e20",
+ "lastOpenFiles": [
+ "problems/1971.寻找图中是否存在路径.md",
+ "README.md"
+ ]
+}

problems/1971.寻找图中是否存在路径.md

@@ -47,11 +47,22 @@ void init() {
  father[i] = i;
  }
 }
-// 并查集里寻根的过程
+// 并查集里寻根的过程，这里递归调用当题目数据过多，递归调用可能会发生栈溢出
+
 int find(int u) {
  return u == father[u] ? u : father[u] = find(father[u]); // 路径压缩
 }
 
+// 使用迭代的方法可以避免栈溢出问题
+int find(int x) {
+ while (x != parent[x]) {
+ // 路径压缩，直接将x链接到其祖先节点，减少树的高度
+ parent[x] = parent[parent[x]];
+ x = parent[x];
+ }
+return x;
+}
+
 // 判断 u 和 v是否找到同一个根
 bool isSame(int u, int v) {
  u = find(u);
@@ -84,6 +95,8 @@ void join(int u, int v) {
 
 此时我们就可以直接套用并查集模板。
 
+本题在join函数调用find函数时如果是递归调用会发生栈溢出提示，建议使用迭代方法
+
 使用 join(int u, int v)将每条边加入到并查集。
 
 最后 isSame(int u, int v) 判断是否是同一个根 就可以了。
@@ -102,8 +115,13 @@ private:
  }
  }
  // 并查集里寻根的过程
- int find(int u) {
- return u == father[u] ? u : father[u] = find(father[u]);
+ int find(int x) {
+ while (x != parent[x]) {
+ // 路径压缩，直接将x链接到其祖先节点，减少树的高度
+ parent[x] = parent[parent[x]];
+ x = parent[x];
+ }
+ return x;
  }
 
  // 判断 u 和 v是否找到同一个根