update

README.md

@@ -23,4 +23,17 @@ struct Status{
 };
 
 std::priority_queue<Status> q;
+```
+
+### [P1330](https://www.luogu.com.cn/problem/P1330)
+#### BFS时注意初始化一开始的去重数组
+```cpp
+void bfs(){
+    for(ll i{1};i<=n;i++){
+        color_sum[1]=color_sum[2]=0;
+        if(vis[i])continue;
+        q.push(i);
+        set_color(i, 1);
+        vis[i]=true; // 注意初始化错误
+        while(!q.empty()){
 ```

src/P1330/P1330.cpp

@@ -1,14 +1,7 @@
-//#define NDEBUG
 #include <iostream>
 #include <vector>
 #include <queue>
 #include <algorithm>
-#define NV(v)#v<<" : "<<(v)
-#ifdef NDEBUG
-#define DEBUG(code)
-#else
-#define DEBUG(code){code}
-#endif
 
 using ll = long long;
 using std::endl;
@@ -22,22 +15,24 @@ static std::vector<ll> next[max_n];
 static bool vis[max_n];
 static std::queue<ll> q;
 static int colors[max_n];
-static ll color_sum[3];
+static ll color_sum[3], ans;
 void set_color(const ll n,const int color)noexcept{
     colors[n]=color;
     color_sum[color]++;
 }
 
 void flush_exit()noexcept{
-    os<<endl;
+    os<<std::flush;
     _Exit(0);
 }
 
 void bfs(){
     for(ll i{1};i<=n;i++){
+        color_sum[1]=color_sum[2]=0;
         if(vis[i])continue;
         q.push(i);
         set_color(i, 1);
+        vis[i]=true; // 注意初始化错误
         while(!q.empty()){
             const auto front = q.front();
             q.pop();
@@ -45,7 +40,7 @@ void bfs(){
             for(const auto i:next[front]){
                 if(vis[i]){
                     if(colors[i]==colors[front]){
-                        os<<"Impossible";
+                        os<<"Impossible\n";
                         flush_exit();
                     }
                     continue;
@@ -55,6 +50,7 @@ void bfs(){
                 q.push(i);
             }
         }
+        ans+=std::min(color_sum[1],color_sum[2]);
     }
 }
 
@@ -67,6 +63,6 @@ int main(){
     }
 
     bfs();
-    os<<std::min(color_sum[1],color_sum[2]);
+    os<<ans<<'\n';
     flush_exit();
 }