圣诞岛的旅行

Problem
Angel最近无聊，去了圣诞岛(CX *^_^*)，他喜欢无目的的乱逛，当然，他不会轻易地回头。Angel想去广场，那么，他什么时候才能到呢？你已经得到了CX的地图，地图上有N(N <= 100)个交叉路口，交叉路口之间有马路相连接(不超过1000条马路)。因为CX的人遵循奇怪的规则，道路都是单向的，不同的道路之间有一定的距离，我们假设Angel所在的地点为点1，广场所在点为N。假设Angel走一单位距离需要一单位时间。问Angel最早和最迟什么时候到达广场？

Input
本题有多组数据，第一行N, M，M是边的数量以后M行，每行3个整数X, Y, Weight，代表一条从X城市到Y城市，长度为Wweight的边。

Output
每组数据，第一行是最少时间，第二行是最迟时间，要是可怜的Angel可能永远到不了广场，输出一行Never。

Sample Input
5 5
1 2 1
1 4 10
2 3 1
3 4 1
4 5 1

Sample Output
4
11

源码：

#include<stdio.h>
#include<assert.h>
#ifdef_DEBUG
#include<stack>//forshowingpath
#endif
#defineMAX_N100
#defineMAX_M1000
#defineCOST_IFINITE-1
intn,m;
struct_List
{
intvertex;
intcost;
_List*next;
};
structVertex_t
{
Vertex_t():cost(COST_IFINITE),parent(0),isVisited(false),head(NULL),worstCost(COST_IFINITE)
{/**/}
_List*head;
intcost;
intparent;
boolisVisited;

intworstParent;
intworstCost;
};
Vertex_tvertics[MAX_N+1];
intmin_cost,max_cost;
Vertex_t*min_who,*max_who;
voidReadGraph(FILE*file)
{
inti=m;
while(i-->0)
{
inta,b,c;
fscanf(file,"%d%d%d/n",&a,&b,&c);
_List*p=new_List;
p->vertex=b;
p->cost=c;
p->next=NULL;
if(vertics[a].head==NULL)
{
vertics[a].head=new_List;
vertics[a].head->vertex=a;
vertics[a].head->next=p;
}else
{
p->next=vertics[a].head->next;
vertics[a].head->next=p;
}
}
}
voidResolve(inttoVisit,intcost,Vertex_t*who)
{
if(toVisit<1||toVisit>n)
return;
if(!vertics[toVisit].isVisited)
{
vertics[toVisit].isVisited=true;
vertics[toVisit].cost=who->cost+cost;
vertics[toVisit].parent=who->head->vertex;

vertics[toVisit].worstCost=who->worstCost+cost;
vertics[toVisit].worstParent=who->head->vertex;
}else
{
if(vertics[toVisit].cost>who->cost+cost)
{
vertics[toVisit].cost=who->cost+cost;
vertics[toVisit].parent=who->head->vertex;
}
if(vertics[toVisit].worstCost<who->worstCost+cost)
{
vertics[toVisit].worstCost=who->worstCost+cost;
vertics[toVisit].worstParent=who->head->vertex;
}else
return;
}
if(toVisit==n)
{
if(!min_who||cost+who->cost<min_cost)
{
min_cost=cost+who->cost;
min_who=who;
}
if(!max_who||who->worstCost+cost>max_cost)
{
max_who=who;
max_cost=who->worstCost+cost;
}
return;
}
_List*p=vertics[toVisit].head->next;
while(p)
{
Resolve(p->vertex,p->cost,&vertics[toVisit]);
p=p->next;
}
}
intmain()
{
vertics[1].cost=0;
vertics[1].worstCost=0;
FILE*fp=fopen("data.dat","rb");
fscanf(fp,"%d%d/n",&n,&m);
ReadGraph(fp);
_List*p=vertics[1].head->next;
while(p)
{
Resolve(p->vertex,p->cost,&vertics[1]);
p=p->next;
}
if(min_who==NULL)
{
printf("Impossible!/n");
return0;
}
printf("min%d/n",min_cost);
if(max_who==NULL)
{
printf("Impossible!/n");
return0;
}
printf("max%d/n",max_cost);

#ifdef_DEBUG
{
Vertex_t*pv=min_who;
usingstd::stack;
stack<int>path;
path.push(n);
while(pv->parent)
{
path.push(pv->head->vertex);
pv=&vertics[pv->parent];
}
path.push(1);
while(path.size()!=0)
{
printf("%d",path.top());
path.pop();
}
printf("/n");
}
{
Vertex_t*pv=max_who;
usingstd::stack;
stack<int>path;
path.push(n);
while(pv->worstParent)
{
path.push(pv->head->vertex);
pv=&vertics[pv->worstParent];
}
path.push(1);
while(path.size()!=0)
{
printf("%d",path.top());
path.pop();
}
printf("/n");
}
#endif//_DEBUG
return0;
}
//data.dat
55
1220
1410
231
3420
451
//output
min11
max42
145
12345
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