【网络流24题】软件补丁问题

题面

https://www.luogu.org/problem/P2761

题解

状态压缩+最短路+动态边（写的是没加动态边的90分版）

话说今年$NOI2019$ $D2$ $T1$ $kd-tree$不写动态边炸成52分。。。

#include<cstdio>
#include<iostream>
#include<cstring>
#include<vector>
#include<queue>
#include<cstdlib>
#define ri register int
#define N (1<<21)
using namespace std;
int n,m;

int d;
int sta;
string s1,s2;
bool vis[N];
int dis[N];
vector<int> to[N],len[N];

void add_edge(int a,int b,int c) {
  to[a].push_back(b); len[a].push_back(c);
}

void link(int cur,int sta) {
  if (cur==n) {
    int ret=sta;
    for (ri i=0;i<n;i++) {
      if (s2[i]=='-' && (ret&(1<<i))) ret^=(1<<i);
      if (s2[i]=='+' && (!(ret&(1<<i)))) ret^=(1<<i);
    }
    if (sta!=ret) add_edge(sta,ret,d);
    return;
  }
  if (s1[cur]=='+') link(cur+1,sta+(1<<cur)); 
    else if (s1[cur]=='-') link(cur+1,sta); 
      else link(cur+1,sta),link(cur+1,sta+(1<<cur));
}

struct node {
  int u,d;
  bool operator < (const node &rhs) const {
    return d>rhs.d;
  }
};

void dijkstra() {
  priority_queue<node> q;
  memset(dis,0x3f,sizeof(dis));
  memset(vis,0,sizeof(vis));
  dis[(1<<n)-1]=0;
  q.push((node){(1<<n)-1,0});
  while (!q.empty()) {
    int x=q.top().u; q.pop();
    if (vis[x]) continue;
    if (x==0) {
      printf("%d
",dis[x]);
      exit(0);
    }
    vis[x]=1;
    for (ri i=0;i<to[x].size();i++) {
      int y=to[x][i];
      if (dis[y]>dis[x]+len[x][i]) {
        dis[y]=dis[x]+len[x][i];
        q.push((node){y,dis[y]});
      }
    }
  }
}

int main(){
  ios::sync_with_stdio(false);
  cin>>n>>m;
  for (ri i=1;i<=m;i++) {
    cin>>d>>s1>>s2;
    link(0,0);
  }
  dijkstra();
  if (dis[0]>1e9) dis[0]=0;
  cout<<dis[0]<<endl;
}