HDU - 6797 Tokitsukaze and Rescue

传送门：HDU - 6797

思路分析

因为边权随机，所以最短路的边很少，直接爆搜就行了，注意pre数组一定不要开全局

AC代码

#include <bits/stdc++.h>
#define fi first
#define se second
#define ll long long
#define pb push_back
#define mp make_pair
#define fun function
#define sz(x) (x).size()
#define lowbit(x) (x)&(-x)
#define all(x) (x).begin(),(x).end()
#define mem(a,b) memset(a,b,sizeof(a))

namespace FastIO {
#define BUF_SIZE 100000
#define OUT_SIZE 100000
    bool IOerror=0;
    inline char nc() {
        static char buf[BUF_SIZE],*p1=buf+BUF_SIZE,*pend=buf+BUF_SIZE;
        if(p1==pend) {
            p1=buf;
            pend=buf+fread(buf,1,BUF_SIZE,stdin);
            if(pend==p1) {
                IOerror=1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch==' '||ch=='\n'||ch=='\r'||ch=='\t';
    }
    template<class T> inline bool read(T &x) {
        bool sign=0;
        char ch=nc();
        x=0;
        for(; blank(ch); ch=nc());
        if(IOerror)return false;
        if(ch=='-')sign=1,ch=nc();
        for(; ch>='0'&&ch<='9'; ch=nc())x=x*10+ch-'0';
        if(sign)x=-x;
        return true;
    }
    template<class T,class... U>bool read(T& h,U&... t) {
        return read(h)&&read(t...);
    }
#undef OUT_SIZE
#undef BUF_SIZE
};
using namespace std;
using namespace FastIO;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int INF = 0x3f3f3f3f;

int n,k,ans;
int e[55][55],dis[55],vis[55];

void spfa(int pre[]){
    mem(dis,INF);
    mem(vis,0);
    mem(pre,0);
    dis[1]=0;
    queue<int>q;
    q.push(1);
    while(!q.empty()) {
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int v=1; v<=n; v++) {
            int w=e[u][v];
            if(dis[v]>dis[u]+w) {
                dis[v]=dis[u]+w;
                pre[v]=u;
                if(!vis[v]) {
                    q.push(v);
                    vis[v]=1;
                }
            }
        }
    }
}

void dfs(int x) {
    int pre[55];
    if(x==k+1) {
        spfa(pre);
        ans=max(ans,dis[n]);
        return ;
    }
    spfa(pre);
    int u=pre[n];
    int v=n;
    while(u) {
        int w=e[u][v];
        e[u][v]=e[v][u]=INF;
        dfs(x+1);
        e[u][v]=e[v][u]=w;
        v=u;
        u=pre[v];
    }
}

int main() {

#ifdef xiaofan
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif

    int T;
    read(T);
    mem(e,INF);
    while(T--) {
        read(n,k);
        ans=0;
        int m=(n-1)*n/2;
        while(m--) {
            int u,v,w;
            read(u,v,w);
            e[u][v]=e[v][u]=w;
        }
        dfs(1);
        printf("%d\n",ans);
    }




    return 0;
}