diff --git a/README.md b/README.md
index 9b6640a..1b807ae 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,8 @@
 # bdfz_2024_summer
+# 竞赛的一些方法
+
+1. 真正难的地方是通过题目给的信息和性质推出要用的算法
+
 # 题目经验总结
 ## Day2
 ### [U111091 区间2段覆盖](./day2/U111091/U111091.md)
@@ -9,9 +13,7 @@
 >隔着老远swap一般不稳定
 >稳定：插入，归并，冒泡
 
-# 竞赛的一些方法
 
-1. 真正难的地方是通过题目给的信息和性质推出要用的算法
 
 ## Day3
 ### [U86432 捞鱼(fish)](./day3/U86432/U86432.md)
@@ -104,4 +106,5 @@ ll ksm(ll a,ll b,ll M){
 >扫描线
 >矩阵乘法
 
-
+## Day9
+### 字典树与异或极值
diff --git a/day9/P2580/P2580.cpp b/day9/P2580/P2580.cpp
new file mode 100644
index 0000000..d9412f1
--- /dev/null
+++ b/day9/P2580/P2580.cpp
@@ -0,0 +1,85 @@
+//AC Code
+#include<bits/stdc++.h>
+using namespace std;
+
+struct Node{
+    bool v=false;
+    bool is_word=false;
+    int next=0;
+};
+
+const int MAXN=1e6;
+int n,tn=0,m;
+Node t[MAXN][26];
+
+int main(int argc,char *argv[]){
+    ios::sync_with_stdio(false);
+    cin.tie(0);
+
+    #ifdef OITEST
+        #define AS(c){if(!(c)){cerr<<"assert faild :"<<#c<<endl;return -1;}}
+        AS(argc==3)
+        cout<<argv[0]<<" "<<argv[1]<<" "<<argv[2]<<endl;
+        ifstream ifile(argv[1]);
+        ifstream afile(argv[2]);
+        AS(ifile.is_open()==true)
+        AS(afile.is_open()==true)
+        stringstream ss;
+        #define cin ifile
+        #define cout ss
+    #endif
+
+    cin>>n;
+    for(int i=1;i<=n;i++){
+        string s;
+        cin>>s;
+        int now=0;
+        for(int j=0;j<s.size()-1;j++){
+            if (t[now][s[j]-'a'].next==0) {
+                t[now][s[j]-'a'].next=++tn;
+            }
+            now=t[now][s[j]-'a'].next;
+        }
+        t[now][s[s.size()-1]-'a'].is_word=true;
+    }
+    cin>>m;
+    for(int i=1;i<=m;i++){
+        string s;
+        cin>>s;
+        int now=0;
+        #ifdef OIPRINT
+            // cout<<s<<endl;
+            #define PRINTV(v)
+        #endif
+        for(int j=0;j<s.size()-1;j++){
+            #ifdef OIPRINT
+                PRINTV(j)
+                PRINTV(now)
+                PRINTV(t[now][s[j]-'a'].next)
+            #endif
+            if (t[now][s[j]-'a'].next==0) {
+                cout<<"WRONG"<<endl;
+                goto out;
+            }
+            now=t[now][s[j]-'a'].next;
+        }
+        if (!t[now][s[s.size()-1]-'a'].is_word) {
+            cout<<"WRONG"<<endl;
+            goto out;
+        }
+        if(t[now][s[s.size()-1]-'a'].v){
+            cout<<"REPEAT"<<endl;
+        }else{
+            t[now][s[s.size()-1]-'a'].v=true;
+            cout<<"OK"<<endl;
+        }
+        out:;
+        #ifdef OITEST
+            string cans;
+            afile>>cans;
+            string myans;
+            ss>>myans;
+            AS(myans==cans)
+        #endif
+    }
+}
\ No newline at end of file
diff --git a/day9/P2580/P2580_1.in b/day9/P2580/P2580_1.in
new file mode 100644
index 0000000..2a13b4e
--- /dev/null
+++ b/day9/P2580/P2580_1.in
@@ -0,0 +1,4 @@
+1
+ad
+1
+a
diff --git a/day9/P2580/P2580_1.out b/day9/P2580/P2580_1.out
new file mode 100644
index 0000000..3367140
--- /dev/null
+++ b/day9/P2580/P2580_1.out
@@ -0,0 +1 @@
+WRONG
diff --git a/day9/P2580/P2580_2.in b/day9/P2580/P2580_2.in
new file mode 100644
index 0000000..2fd2bc2
--- /dev/null
+++ b/day9/P2580/P2580_2.in
@@ -0,0 +1,10 @@
+5  
+a
+b
+c
+ad
+acd
+3
+a
+a
+e
\ No newline at end of file
diff --git a/day9/P2580/P2580_2.out b/day9/P2580/P2580_2.out
new file mode 100644
index 0000000..68d2cc3
--- /dev/null
+++ b/day9/P2580/P2580_2.out
@@ -0,0 +1,3 @@
+OK
+REPEAT
+WRONG
\ No newline at end of file
diff --git a/xmake.lua b/xmake.lua
index cd424f7..fdc5a39 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -87,4 +87,12 @@ target("U279656")
     for v=1,3 do
         local s=tostring(v)
         add_tests(s,{files="./day8/U279656/*.cpp",runargs={"seg"..s..".in","seg"..s..".ans"},defines="OITEST",run_timeout=1000})
-    end
\ No newline at end of file
+    end
+
+    target("P2580")
+        set_rundir("./day9/P2580")
+        add_files("./day9/P2580/*.cpp")
+        for v=1,2 do
+            local s=tostring(v)
+            add_tests(s,{files="./day9/P2580/*.cpp",runargs={"P2580_"..s..".in","P2580_"..s..".out"},defines="OITEST",run_timeout=1000})
+        end 
\ No newline at end of file