洛谷-P2761 软件补丁问题

软件补丁问题

状态压缩 + 最短路

对于当前 bug 的状态，可以作为一个点，表示的方式用状态压缩的方式，接着边就是通过一个补丁，转换到另外一个 bug 状态

直接最短路，dijkstra 或 bfs 或 SPFA 都可

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <queue>
using namespace std;
typedef long long ll;
const int maxn = 1 << 20 | 1;
const ll inf = 1e17 + 10;
ll vis[maxn];
ll pre[110][2], nex[110][2], t[110];
int n, m;

struct node
{
    ll u, val;
    node(){}
    node(ll _u, ll _val){u = _u; val = _val;}
    bool operator < (const node& a) const
    {
        return a.val < val;
    }
};

ll dijkstra(ll s)
{
    priority_queue<node>q;
    q.push({s, 0ll});
    while(q.size())
    {
        node now = q.top();
        q.pop();
        if(vis[now.u]) continue;
        vis[now.u] = 1;
        if(now.u == 0) return now.val;
        for(int i=0; i<m; i++)
        {
            ll temp = now.u;
            temp |= nex[i][0];
            temp |= nex[i][1];
            temp ^= nex[i][1];
            if(vis[temp] == 0 && (now.u & pre[i][0]) == pre[i][0] && (now.u & pre[i][1]) == 0)
                q.push({temp, now.val + t[i]});
        }
    }
    return inf;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    ll len = (1 << n) - 1;
    for(int i=0; i<m; i++)
    {
        cin >> t[i];
        string s;
        cin >> s;
        for(int k=0; k<2; k++)
        {
            pre[i][k] = 0;
            char x = k == 0 ? '+' : '-';
            for(int j=0; j<n; j++)
            {
                pre[i][k] <<= 1;
                pre[i][k] += x == s[j];
            }
        }
        cin >> s;
        for(int k=0; k<2; k++)
        {
            nex[i][k] = 0;
            char x = k == 0 ? '+' : '-';
            for(int j=0; j<n; j++)
            {
                nex[i][k] <<= 1;
                nex[i][k] += x == s[j];
            }
        }
    }
    ll ans = dijkstra((1 << n) - 1);
    if(ans == inf) ans = 0;
    cout << ans << endl;
    return 0;
}

标签：P2761,洛谷,vis,int,ll,补丁,include,now
来源： https://www.cnblogs.com/dgsvygd/p/16393492.html