poj 3013 Big Christmas Tree (spf…
2013-04-23 09:23
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题意:要建一棵圣诞树,使得总的花费最小。具体规则是:圣诞树是一颗无向树形图,其中,编号为1的节点为根节点,原始图中每条边具有边权(unit):材料的单位价值,每个点也有一个权(weight):点的重量。总的花费则是生成树中所有点的花费之和。
而每个点的花费为 根结点到该点的距离(边权unit)* 该点的重量。
思路:求出各点的最短路径 再与点的重量相乘之和; 注意两点我觉得,inf 要定义足够大,10个9吧,还有,用memset
初始化会严重超时,不用竟然才600多MS 。。。。这个我无语了。。。。
#include <stdio.h>
#include <string.h>
#define VM 50005
#define EM 100005
#define inf 9999999999
int head[VM],ep;
int weigt[VM];
struct dege
{
int
v,w,next;
} e[EM];
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;
}
__int64 spfa (int n)
{
int
vis[VM],queue[VM],cnt[VM];
__int64
dis[VM];
//memset
(vis,0,sizeof(vis));
//memset
(cnt,0,sizeof(cnt));
// memset
(dis,0x3f,sizeof(dis));
for (int i =
1; i <= n; i ++)
{
cnt[i] = 0;
vis[i] = 0;
dis[i] = inf;
}
dis[1] =
0;
int front =
-1,rear = 0;
queue[rear++] = 1;
vis[1] =
1;
cnt[1] =
1;
while (front
!= rear)
{
front = (front+1)%(n+1);
int u = queue[front];
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)
{
dis[v] = dis[u] + e[i].w;
if (!vis[v])
{
vis[v] = 1;
queue[rear] = v;
rear = (rear+1)%(n+1);
cnt[v] ++;
if (cnt[v] >= n)
return 0;
}
}
}
}
__int64 ans
= 0;
for (int i =
2; i <= n; i ++)
{
if (dis[i] == inf)
return 0;
ans += weigt[i]*dis[i];
}
return
ans;
}
int main ()
{
int
t,n,m,v1,v2,cost;
scanf
("%d",&t);
while (t
--)
{
ep = 0;
memset (head,-1,sizeof(head));
scanf ("%d%d",&n,&m);
if (n == 0)
{
for (int i = 1; i <= m; i ++)
scanf
("%d%d%d",&v1,&v2,&cost);
printf ("0\n");
}
else if (n == 1)
{
scanf ("%d",&cost);
for (int i = 1; i <= m; i ++)
scanf
("%d%d%d",&v1,&v2,&cost);
printf ("0\n");
}
else
{
for (int i = 1; i <= n; i ++)
scanf ("%d",&weigt[i]);
while (m --)
{
scanf
("%d%d%d",&v1,&v2,&cost);
addedge (v1,v2,cost);
addedge (v2,v1,cost);
}
__int64 ans = spfa (n);
if (!ans)
printf ("No Answer\n");
else
printf ("%I64d\n",ans);
}
}
return
0;
}
而每个点的花费为 根结点到该点的距离(边权unit)* 该点的重量。
思路:求出各点的最短路径 再与点的重量相乘之和; 注意两点我觉得,inf 要定义足够大,10个9吧,还有,用memset
初始化会严重超时,不用竟然才600多MS 。。。。这个我无语了。。。。
#include <stdio.h>
#include <string.h>
#define VM 50005
#define EM 100005
#define inf 9999999999
int head[VM],ep;
int weigt[VM];
struct dege
{
int
v,w,next;
} e[EM];
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;
}
__int64 spfa (int n)
{
int
vis[VM],queue[VM],cnt[VM];
__int64
dis[VM];
//memset
(vis,0,sizeof(vis));
//memset
(cnt,0,sizeof(cnt));
// memset
(dis,0x3f,sizeof(dis));
for (int i =
1; i <= n; i ++)
{
cnt[i] = 0;
vis[i] = 0;
dis[i] = inf;
}
dis[1] =
0;
int front =
-1,rear = 0;
queue[rear++] = 1;
vis[1] =
1;
cnt[1] =
1;
while (front
!= rear)
{
front = (front+1)%(n+1);
int u = queue[front];
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)
{
dis[v] = dis[u] + e[i].w;
if (!vis[v])
{
vis[v] = 1;
queue[rear] = v;
rear = (rear+1)%(n+1);
cnt[v] ++;
if (cnt[v] >= n)
return 0;
}
}
}
}
__int64 ans
= 0;
for (int i =
2; i <= n; i ++)
{
if (dis[i] == inf)
return 0;
ans += weigt[i]*dis[i];
}
return
ans;
}
int main ()
{
int
t,n,m,v1,v2,cost;
scanf
("%d",&t);
while (t
--)
{
ep = 0;
memset (head,-1,sizeof(head));
scanf ("%d%d",&n,&m);
if (n == 0)
{
for (int i = 1; i <= m; i ++)
scanf
("%d%d%d",&v1,&v2,&cost);
printf ("0\n");
}
else if (n == 1)
{
scanf ("%d",&cost);
for (int i = 1; i <= m; i ++)
scanf
("%d%d%d",&v1,&v2,&cost);
printf ("0\n");
}
else
{
for (int i = 1; i <= n; i ++)
scanf ("%d",&weigt[i]);
while (m --)
{
scanf
("%d%d%d",&v1,&v2,&cost);
addedge (v1,v2,cost);
addedge (v2,v1,cost);
}
__int64 ans = spfa (n);
if (!ans)
printf ("No Answer\n");
else
printf ("%I64d\n",ans);
}
}
return
0;
}
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