update

CMakeLists.txt

@@ -34,3 +34,7 @@ add_executable(P1311 ${CMAKE_CURRENT_LIST_DIR}/P1311/P1311.cpp)
 add_executable(P4017 ${CMAKE_CURRENT_LIST_DIR}/P4017/P4017.cpp)
 
 add_executable(P2782 ${CMAKE_CURRENT_LIST_DIR}/P2782/P2782.cpp)
+
+add_executable(P1091 ${CMAKE_CURRENT_LIST_DIR}/P1091/P1091.cpp)
+
+add_executable(P1020 ${CMAKE_CURRENT_LIST_DIR}/P1020/P1020.cpp)

P1020/P1020.cpp

@@ -0,0 +1,16 @@
+#include <iostream>
+
+using std::cin, std::cout, std::iostream;
+
+constexpr size_t MAX_N {(size_t)5e4+5};
+int n, arr[MAX_N], len[MAX_N], ans1, ans2;
+
+int main(){
+    iostream::sync_with_stdio(false), cin.tie(0), cout.tie(0);
+
+    cin>>n;
+    for(size_t i=0;i<n;i++){
+        cin>>arr[i];
+    }
+
+}

P1091/P1091.cpp

@@ -0,0 +1,35 @@
+#include <iostream>
+#include <algorithm>
+
+using std::cin,std::cout,std::max,std::iostream;
+
+constexpr size_t MAX_N {100+5};
+int n, arr[MAX_N], go_up[MAX_N], go_down[MAX_N], ans;
+
+int main(){
+    iostream::sync_with_stdio(false),cin.tie(0),cout.tie(0);
+
+    cin>>n;
+    for(int i=0;i<n;i++){
+        cin>>arr[i];
+        go_up[i]=1,go_down[i]=1;
+    }
+    for(int i=0;i<n;i++){//j < i
+        for(int j=i-1;j>=0;j--){
+            if(arr[j]<arr[i] && go_up[i]<go_up[j]+1){
+                go_up[i] = go_up[j]+1;
+            }
+        }
+    }
+    for(int i=n-1;i>=0;i--){//i < j
+        for(int j=i+1;j<n;j++){
+            if(arr[j]<arr[i] && go_down[i]<go_down[j]+1){
+                go_down[i] = go_down[j] + 1;
+            }
+        }
+    }
+    for(int i=0;i<n;i++){
+        ans = max(ans,go_down[i]+go_up[i]-1);
+    }
+    cout<<n-ans<<'\n';
+}