poj2377
最大生成树，注意边数组开二倍大小。注意不连通输出－1；
View Code
#include
<
iostream
>
#include
<
cstdio
>
#include
<
cstdlib
>
#include
<
cstring
>
#include
<
queue
>
using
namespace
std;
#define
maxn 1005
#define
maxm 20005
struct
Edge
{
int
v, next, w;
Edge(
int
vv,
int
nn,
int
ww) :
v(vv), next(nn), w(ww)
{
}
Edge()
{
}
} edge[maxm
*
2
];
int
head[maxn], count;
bool
vis[maxn];
int
ans
=
0
;
int
m, n;
bool
operator
<
(
const
Edge
&
a,
const
Edge
&
b)
{
return
a.w
<
b.w;
}
void
addedge(
int
u,
int
v,
int
w)
{
edge[count].next
=
head[u];
edge[count].v
=
v;
edge[count].w
=
w;
head[u]
=
count;
count
++
;
}
void
input()
{
scanf(
"
%d%d
"
,
&
n,
&
m);
for
(
int
i
=
0
; i
<
m; i
++
)
{
int
a, b, c;
scanf(
"
%d%d%d
"
,
&
a,
&
b,
&
c);
a
--
, b
--
;
addedge(a, b, c);
addedge(b, a, c);
}
}
void
prim(
int
src)
{
priority_queue
<
Edge
>
pq;
int
pre
=
0
;
Edge temp;
pq.push(Edge(src,
0
,
0
));
while
(
!
pq.empty())
{
do
{
temp
=
pq.top();
pq.pop();
}
while
(
!
pq.empty()
&&
vis[temp.v]);
if
(vis[temp.v])
return
;
vis[temp.v]
=
true
;
pre
=
temp.v;
ans
+=
temp.w;
for
(
int
i
=
head[pre]; i
!=
-
1
; i
=
edge[i].next)
if
(
!
vis[edge[i].v])
pq.push(edge[i]);
}
}
int
main()
{
//
freopen("t.txt", "r", stdin);
memset(head,
-
1
,
sizeof
(head));
memset(vis,
0
,
sizeof
(vis));
count
=
0
;
input();
prim(
0
);
bool
ok
=
true
;
for
(
int
i
=
0
; i
<
n; i
++
)
if
(
!
vis[i])
{
ok
=
false
;
break
;
}
if
(ok)
printf(
"
%d\n
"
, ans);
else
printf(
"
%d\n
"
,
-
1
);
return
0
;
}