eoj 2104 (提问：请帮忙解答下我的问题哈)
http://202.120.80.191/problem.php?problemid=2104
这道题是最短路的变形，只要修改下状态方程，如果用最短路用堆优化,dist同样是每次都要更新
dist[tmp->v]=max(dist[tmp->v],min(dist[it],tmp->w));
我用stl的堆，但是一直出问题，所以能不能帮我看下一下问题是怎么出的
#include
<
iostream
>
#include
<
algorithm
>
#define min(a,b) ((a)
<
(b)?(a):(b))#define max(a,b) ((a)
>
(b)?(a):(b))using namespace std;#define MaxM
1000005
#define MaxN
100005
#define MaxW
2000000005
int
dist[MaxN];
//
dist上存储的是扩展当前这个点是的可携带的最大负重struct node{
int
v,w; node
*
next
; node() { w
=
v
=
0
;
next
=
0
;}};node
*
V[MaxN];
int
flag[MaxN];
int
heap[
2
*
MaxN],hsize;
int
N,M;bool cmp(
int
a,
int
b){ return dist[a]
<
dist[b];}void solve(
int
s,
int
t){
int
it,i; node
*
tmp; dist[s]
=
MaxW; hsize
=
1
; heap[
0
]
=
s; make_heap(heap,heap
+
hsize,cmp);
while
(!flag[t]){
if
(!hsize)break; it
=
heap[
0
]; pop_heap(heap,heap
+
hsize); hsize
--
;
if
(flag[it]
==
1
)continue; flag[it]
=
1
;
for
(tmp
=
V[it];tmp!
=
0
;tmp
=
tmp
->
next
)
if
(!flag[tmp
->
v]){ dist[tmp
->
v]
=
max(dist[tmp
->
v],min(dist[it],tmp
->
w));
//
更新dist的值 heap[hsize
++
]
=
tmp
->
v; push_heap(heap,heap
+
hsize,cmp);} make_heap(heap,heap
+
hsize,cmp);
//
按理说这里是不用make_heap的
//
因为在上面一行中push_heap会调整堆，但是我这个程序就是不行，我实在不知道问什么，push_heap能插入，但是并没
//
实现最大堆，逼得我没办法要加上个重新建堆，但是加上这个后速度爆满，本来这个写法只能勉强过，我加上他后只能超时了，希望高人指点，为什么我这里堆的使用就是会出现这种问题 } printf(
"
%d\n
"
,dist[t]);}void delete_V(node
*
p){
if
(p
==
NULL
)return; delete_V(p
->
next
); delete(p);}
int
main(){
int
u,v,w,s,t,i; node
*
tmp;
while
(scanf(
"
%d%d
"
,
&
N,
&
M)!
=
EOF
&&
N
&&
M){ memset(heap,
0
,sizeof(heap)); memset(dist,
0
,sizeof(dist)); memset(flag,
0
,sizeof(flag)); memset(V,
0
,sizeof(V));
for
(i
=
0
;i
<
M;i
++
){ scanf(
"
%d%d%d
"
,
&
u,
&
v,
&
w); tmp
=
(node
*
)malloc(sizeof(node)); tmp
->
v
=
v; tmp
->
w
=
w; tmp
->
next
=
V[u]; V[u]
=
tmp; tmp
=
(node
*
)malloc(sizeof(node)); tmp
->
v
=
u; tmp
->
w
=
w; tmp
->
next
=
V[v]; V[v]
=
tmp; } scanf(
"
%d%d
"
,
&
s,
&
t); solve(s,t);
for
(i
=
1
;i
<=
N;i
++
) delete_V(V[i]); } return
0
;}
后面实在没办法，该并查集的做法，用并查集确实简单很多，以下是我的代码
#include
<
iostream
>
#include
<
algorithm
>
#define MaxM
1000005
#define MaxN
100005
using namespace std;struct eNode{
int
begin,
end
,w;}E[MaxM];struct node{
int
parent,rank;}V[MaxN];
int
N,M;bool cmp(eNode a,eNode b){ return a.w
>
b.w;}void make_set(){
for
(
int
i
=
1
;i
<=
N;i
++
){ V[i].parent
=
i; V[i].rank
=
0
;}}
int
find(
int
i){
if
(V[i].parent!
=
i) return V[i].parent
=
find(V[i].parent);
else
return i;}void union_set(
int
a,
int
b){
int
fa,fb; fa
=
find(a); fb
=
find(b);
if
(V[fa].rank
<
V[fb].rank)V[fa].parent
=
fb;
else
{ V[fb].parent
=
fa;
if
(V[fa].rank
==
V[fb].rank)
++
V[fa].rank; }}void solve(
int
s,
int
t){
int
i,u,v; make_set();
for
(i
=
0
;i
<
M;i
++
){ u
=
E[i].begin; v
=
E[i].end;
if
(find(u)
==
find(v))continue; union_set(u,v);
if
(find(s)
==
find(t)){ printf(
"
%d\n
"
,E[i].w); return;} }}
int
main(){
int
i,u,v,w,s,t;
while
(scanf(
"
%d%d
"
,
&
N,
&
M)!
=
EOF){ memset(E,
0
,sizeof(E));
for
(i
=
0
;i
<
M;i
++
){ scanf(
"
%d%d%d
"
,
&
u,
&
v,
&
w); E[i].begin
=
u; E[i].end
=
v; E[i].w
=
w; } sort(E,E
+
M,cmp); scanf(
"
%d%d
"
,
&
s,
&
t); solve(s,t); } return
0
;}