学步园

如样例：

3 6

 2 4


0 2


4 7

所对应的序列为：1 2 4 5

思路： dis[i] 表示 [0,i）中的元素个数，所以有 dis[v]-dis[u] >= 2
还有个隐含条件 1>=dis[i+1]-dis[i]>=0
用spfa 实现，因为有负环所以用栈结构，队列是457MS 栈是32MS

852K   
32MS

#include <stdio.h>
#include <string.h>
#define EM 40000
#define VM 10005
#define inf -10000000
struct edge
{
    int
v,w,next;
}e[EM];
int head[VM],ep;

void addedge(int cu,int cv,int cw)
{
    ep ++;
    e[ep].v =
cv;
    e[ep].w =
cw;
    e[ep].next =
head[cu];
    head[cu] =
ep;
}
int maxn (int a,int b)
{
    return a
> b?a:b;
}

void spfa (int n)
{
    int
vis[VM],dis[VM],stack[EM];
    memset
(vis,0,sizeof(vis));
    memset
(dis,-1,sizeof(dis));
    dis[n+2] =
0;    
//超级源点
    int top =
1;
    vis[n+2] =
1;
    stack[0] =
n+2;
    while
(top)
    {
       
int u = stack[--top];
       
vis[u] = 0;
       
for (int i = head[u];i != -1;i = e[i].next)
       
{
           
int v = e[i].v;
           
if (dis[v] < dis[u] +
e[i].w)   //松驰
           
{
               
dis[v] = dis[u] + e[i].w;
               
if (!vis[v])
               
{
                   
vis[v] = 1;
                   
stack[top++] = v;
               
}
           
}
       
}
    }
    printf
("%d\n",dis[n]);
}
int main ()
{
    int
n,v1,v2,m;
    ep =
0;