diff --git a/.gitignore b/.gitignore
index dd155ab..40b11b9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -38,3 +38,4 @@ tempCodeRunnerFile
 tempCodeRunnerFile.cpp
 day3/afternoon/test
 day3/afternoon/operator
+day3/T490194/T490194
diff --git a/README.md b/README.md
index 00de987..e78c68d 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,35 @@
 ## Day3
 ### [U86432 捞鱼(fish)](./day3/U86432/U86432.md)
 1. 数据离散化是指把数据只保留有用的东西，在本题当中指的是把数据排序后保存顺序关系，让内存数组可以少一些
+2. 看到哪个东西的数据量最少，实在不行就从那个东西下手
+
+### [T490194 还原排列](./day3/T490194/T490194.md)
+1. 学会使用`bool next_permutation(begin,end)` 进行排列组合，没有下一个组合时会返回false，下面是一个示例
+```cpp
+#include<bits/stdc++.h>
+using namespace std;
+typedef unsigned int u32;
+ostream& operator<<(ostream &os,const vector<int> &v){
+    os<<"vector<int> [";
+    for(u32 i=0;i<v.size();i++){
+        os<<v[i]<<(i!=v.size()-1?",":"]");
+    }
+    return os;
+}
+int n;
+int main(){
+    cin>>n;
+    vector<int> v(n);
+    for(int &i:v){
+        cin>>i;
+    }
+    cout<<"v:"<<v<<endl;
+    while(next_permutation(v.begin(),v.end())){
+        cout<<"v_pered"<<v<<endl;
+    }
+    
+}
+```
 
 # 排序
 ## 稳定性
diff --git a/day3/T490194/T490194.cpp b/day3/T490194/T490194.cpp
index 3715b93..1d5482e 100644
--- a/day3/T490194/T490194.cpp
+++ b/day3/T490194/T490194.cpp
@@ -1,13 +1,23 @@
 #include<bits/stdc++.h>
 using namespace std;
-
-int n,m;
-
+typedef unsigned int u32;
+ostream& operator<<(ostream &os,const vector<int> &v){
+    os<<"vector<int> [";
+    for(u32 i=0;i<v.size();i++){
+        os<<v[i]<<(i!=v.size()-1?",":"]");
+    }
+    return os;
+}
+int n;
 int main(){
-    cin.sync_with_stdio(false);
-    cin.tie(0);
-
+    cin>>n;
     vector<int> v(n);
-
+    for(int &i:v){
+        cin>>i;
+    }
+    cout<<"v:"<<v<<endl;
+    while(next_permutation(v.begin(),v.end())){
+        cout<<"v_pered"<<v<<endl;
+    }
     
 }
\ No newline at end of file