lightoj 1074

这题怎么说呢，负环上的点都不行

网上也有很多解法

我用dfs的spfa解的

我发现网上别人的代码都是用bfs的spfa写的，我就用的dfs的，快了好多

代码还看的别人的，只有中间的spfa是自己写的

我自己原来写的不知道为什么就过不了

把别人的spfa换成自己的就过了

这个是ac的：

#include<iostream>
#include<cstring>
#include<cmath>
#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
using namespace std;

const int N = 209;
const int MAX = 0x3f3f3f3f;
int dis[N];
int p[N];
int h[N];
int cnt[N];
bool vis[N];
bool r[N];
int c[N];

struct Node
{
    int u, v, w, next;
}e[N*N];

void dfs(int x)
{
    r[x] = 1;
    for(int i=h[x]; i!=-1; i=e[i].next)
        if(!r[e[i].v])
            dfs(e[i].v);
}

void spfa(int u)
{
    if(r[u])
        return ;
    vis[u] = true;
    for(int i = h[u]; i != -1; i = e[i].next)
    {
        int v,w;
        v = e[i].v;
        w = e[i].w;
        if(dis[v] > dis[u] + w)
        {
            dis[v] = dis[u]+w;
            if(vis[v])
            {
                dfs(v);
                return ;
            }
            else
            {
                spfa(v);
            }
        }
    }
    vis[u] = false;
}

int main()
{
    int T;
    scanf("%d", &T);
    for(int tt=1; tt<=T; tt++)
    {
        int n, m;
        scanf("%d", &n);
        memset(cnt, 0, sizeof(cnt));
        memset(vis, 0, sizeof(vis));
        memset(r, 0, sizeof(r));
        memset(dis, 0x3f3f3f3f, sizeof(dis));
        for(int i=1; i<=n; i++)
            scanf("%d", &p[i]);
        scanf("%d", &m);
        memset(h, -1, sizeof(h));
        for(int i=0; i<m; i++)
        {
            int a, b;
            scanf("%d%d", &a, &b);
            e[i].u = a;
            e[i].v = b;
            e[i].w = (p[b]-p[a])*(p[b]-p[a])*(p[b]-p[a]);
            e[i].next = h[a];
            h[a] = i;
        }
        int Q;
        scanf("%d", &Q);
        for(int i=0; i<Q; i++)
            scanf("%d", &c[i]);
        printf("Case %d:
", tt);

        dis[1] = 0;
        spfa(1);
        for(int i=0; i<Q; i++)
        {
            int to = c[i];
            if(dis[to]==MAX || r[to] || dis[to] < 3)
                printf("?
");
            else
                printf("%d
", dis[to]);
        }
    }
    return 0;
}

这个是wa的，那位dalao帮我抓抓虫啊，真的苦，我看了半天楞是没看出来

#include <iostream>
#include <cstdio>
#include <queue>
#include <cstring>
#include <vector>
#include <cmath>
#include <algorithm>
using namespace std;
const int maxn = 250;
const int INF = 0x3f3f3f3f;
int n,m;
int cnt;
struct node
{
    int v,w;
};
bool vis[maxn];
int head[maxn];
int nex[maxn];
node e[maxn*maxn];
int dis[maxn];
int busy[maxn];
bool vis2[maxn];
int c[maxn];
void adde(int u,int v,int w)
{
    node t;
    t.v = v;
    t.w = w;
    e[cnt] = t;
    nex[cnt] = head[u];
    head[u] = cnt ++;
}
void spfa(int u);
void dfs(int u);
int main()
{
    int t;
    scanf("%d",&t);
    for(int k = 1; k <= t; ++k)
    {
        memset(vis2,0,sizeof(vis2));
        memset(dis,0x3f,sizeof(dis));
        memset(vis,0,sizeof(vis));
        memset(head,-1,sizeof(head));
        //memset(cn,0,sizeof(cn));
        memset(nex,-1,sizeof(nex));
        memset(e,0,sizeof(e));
        cnt = 0;
        scanf("%d",&n);
        for(int i = 1; i <= n; ++i)
            scanf("%d",busy+i);

        scanf("%d",&m);
        for(int i = 0; i < m; ++i)
        {
            int a,b;
            scanf("%d%d",&a,&b);
            int c = (busy[b] - busy[a])*(busy[b] - busy[a])*(busy[b] - busy[a]);
            adde(a,b,c);
        }
        int Q;
        scanf("%d",&Q);
        for(int i = 0; i < Q; ++i)
            scanf("%d",c+i);

        printf("Case %d:
", k);
        dis[1] = 0;
        spfa(1);
        for(int i = 0; i < Q; ++i)
        {
            if(dis[c[i]] == INF || vis2[c[i]] || dis[c[i]] < 3)
                printf("?
");
            else
                printf("%d
",dis[c[i]]);
        }
    }
    return 0;
}
void spfa(int u)
{
    if(vis2[u])
        return ;
    vis[u] = true;
    for(int i = head[u]; i != -1; i = nex[i])
    {
        int v,w;
        v = e[i].v;
        w = e[i].w;
        if(dis[v] > dis[u] + w)
        {
            dis[v] = dis[u]+w;
            if(vis[v])
            {
                dfs(v);
                return ;
            }
            else
            {
                spfa(v);
            }
        }
    }
    vis[u] = false;
}
void dfs(int u)
{
    vis2[u] = true;
    for(int i = head[u]; i != -1; i = nex[i])
    {
        int v = e[i].v;
        if(vis2[v] == false)
            dfs(v);
    }
}