poj3268
又犯了同样的错误，开edge数组开小了，应该是maxm,开成了maxn
正反两个图，进行两次dijkstra即可
View Code
#include
<
cstdio
>
#include
<
iostream
>
#include
<
cstdlib
>
#include
<
cstring
>
using
namespace
std;
#define
maxn 1005
#define
maxm 100005
#define
inf 1000000000
struct
Edge
{
int
v, w, next;
}edge[maxm], opedge[maxm];
int
n, m, t, head[maxn], ophead[maxn];
int
tot, optot, len[maxn], oplen[maxn];
void
init()
{
tot
=
0
;
optot
=
0
;
memset(head,
-
1
,
sizeof
(head));
memset(ophead,
-
1
,
sizeof
(ophead));
scanf(
"
%d%d%d
"
,
&
n,
&
m,
&
t);
t
--
;
for
(
int
i
=
0
; i
<
m; i
++
)
{
int
a, b, c;
scanf(
"
%d%d%d
"
,
&
a,
&
b,
&
c);
a
--
;
b
--
;
edge[tot].next
=
head[a];
head[a]
=
tot;
edge[tot].v
=
b;
edge[tot].w
=
c;
tot
++
;
opedge[optot].next
=
ophead[b];
ophead[b]
=
optot;
opedge[optot].v
=
a;
opedge[optot].w
=
c;
optot
++
;
}
}
void
dijkstra(
int
head[], Edge edge[],
int
len[])
{
bool
visited[maxn];
memset(visited,
0
,
sizeof
(visited));
len[t]
=
0
;
while
(
1
)
{
int
best
=
inf, besti
=
-
1
;
for
(
int
i
=
0
; i
<
n; i
++
)
{
if
(len[i]
<
best
&&
!
visited[i])
{
best
=
len[i];
besti
=
i;
}
}
if
(besti
==
-
1
)
break
;
visited[besti]
=
true
;
for
(
int
i
=
head[besti]; i
!=
-
1
; i
=
edge[i].next)
{
int
v
=
edge[i].v;
int
w
=
edge[i].w;
if
(len[v]
>
len[besti]
+
w)
len[v]
=
len[besti]
+
w;
}
}
}
int
main()
{
//
freopen("D:\\t.txt", "r", stdin);
init();
for
(
int
i
=
0
; i
<
n; i
++
)
{
len[i]
=
oplen[i]
=
inf;
}
dijkstra(head, edge, len);
dijkstra(ophead, opedge, oplen);
int
best
=
0
;
for
(
int
i
=
0
; i
<
n; i
++
)
if
(best
<
len[i]
+
oplen[i])
best
=
len[i]
+
oplen[i];
printf(
"
%d\n
"
, best);
return
0
;
}