From c1dc73f77230c54fced44e9d070eddd52dbde48c Mon Sep 17 00:00:00 2001
From: Zengtudor <zengtudor@outlook.com>
Date: Fri, 30 Aug 2024 18:04:27 +0800
Subject: [PATCH] update

---
 20240830/P2661/P2661.cpp | 50 ++++++++++++++++++++++++++++++++++++++++
 20240830/P4089/P4089.cpp | 40 ++++++++++++++++++++++++++++++++
 xmake.lua                |  9 +++++++-
 3 files changed, 98 insertions(+), 1 deletion(-)
 create mode 100644 20240830/P2661/P2661.cpp
 create mode 100644 20240830/P4089/P4089.cpp

diff --git a/20240830/P2661/P2661.cpp b/20240830/P2661/P2661.cpp
new file mode 100644
index 0000000..30f5800
--- /dev/null
+++ b/20240830/P2661/P2661.cpp
@@ -0,0 +1,50 @@
+#include <algorithm>
+#include <iostream>
+#include <queue>
+const int MAX_N{int(2e5+5)};
+
+int in_degree[MAX_N]{},n,next[MAX_N];
+std::queue<int> q;
+bool vis[MAX_N];
+
+int main(){
+    std::cin>>n;
+    for(int i=1;i<=n;i++){
+        int input;
+        std::cin>>input;
+        in_degree[input]++;
+        next[i]=input;
+    }
+    for(int i=1;i<=n;i++){
+        if(in_degree[i]==0){
+            q.push(i);
+        }
+    }
+    
+    while(q.empty()==false){
+        int top = q.front();
+        in_degree[next[top]]--;
+        q.pop();
+        if(in_degree[next[top]]==0){
+            q.push(next[top]);
+        }
+    }
+
+    int ans{0};
+
+    for(int i=1;i<=n;i++){
+        if(in_degree[i]!=0 && vis[i]==false){
+            int begin{i},s{1};
+            int now{next[begin]};
+            vis[begin]=true;
+            while(now!=begin){
+                vis[now]=true;
+                s++;
+                now=next[now];
+            }
+            ans=std::max(ans,s);
+        }
+    }
+
+    std::cout<<ans<<"\n";
+}
\ No newline at end of file
diff --git a/20240830/P4089/P4089.cpp b/20240830/P4089/P4089.cpp
new file mode 100644
index 0000000..0254b97
--- /dev/null
+++ b/20240830/P4089/P4089.cpp
@@ -0,0 +1,40 @@
+#include <iostream>
+#include <queue>
+const int MAX_N{int(1e5+5)};
+
+int in_degree[MAX_N]{},n,next[MAX_N];
+std::queue<int> q;
+
+void find(int num){
+    
+}
+
+int main(){
+    std::cin>>n;
+    for(int i=1;i<=n;i++){
+        int input;
+        std::cin>>input;
+        in_degree[input]++;
+        next[i]=input;
+    }
+    int zero_in_degree_dir = -1;
+    int cnt{};
+    for(int i=1;i<=n;i++){
+        if(in_degree[i]==0){
+            q.push(i);
+            cnt++;
+        }
+    }
+    
+    while(q.empty()==false){
+        int top = q.front();
+        in_degree[next[top]]--;
+        q.pop();
+        if(in_degree[next[top]]==0){
+            q.push(next[top]);
+            cnt++;
+        }
+    }
+
+    std::cout<<(n-cnt)<<"\n";
+}
\ No newline at end of file
diff --git a/xmake.lua b/xmake.lua
index 32030f4..234c957 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -7,6 +7,7 @@ if is_mode("release") then
     add_cxxflags("-march=native")
 end 
 set_languages("c++17")
+set_warnings("all")
 
 target("P1158")
     set_rundir("20240821/P1158")
@@ -28,4 +29,10 @@ target("P2615")
     add_files("20240828/P2615/P2615.cpp")
 
 target("B4015")
-    add_files("20240829/B4015/B4015.cpp")
\ No newline at end of file
+    add_files("20240829/B4015/B4015.cpp")
+
+target("P4089")
+    add_files("20240830/P4089/P4089.cpp")
+
+target("P2661")
+    add_files("20240830/P2661/P2661.cpp")
\ No newline at end of file