Power Network--POJ 1459
1、题目类型：图论、最大流、Edmonds_Karp算法。
2、解题思路：简单最大流问题，Edmonds_Karp算法的经典应用。
3、注意事项：对比Ford_Fulkerson算法DFS寻找增广路径，Edmonds_Karp算法BFS寻找增广路径效率更高。
4、实现方法:
#include
<
iostream
>
#include
<
cmath
>
#include
<
queue
>
using
namespace
std;
#define
Max 110
#define
INF 99999999
int
n,np,nc,m,s,t;
int
map[Max][Max],tmp[Max],pre[Max];
void
Init()
{
int
i,u,v,z;
char
ch;
memset(map,
0
,
sizeof
(map));
cin
>>
np
>>
nc
>>
m;
for
(i
=
0
;i
<
m;i
++
)
{
cin
>>
ch
>>
u
>>
ch
>>
v
>>
ch
>>
z;
map[u
+
1
][v
+
1
]
=
z;
}
for
(i
=
0
;i
<
np;i
++
)
{
cin
>>
ch
>>
u
>>
ch
>>
z;
map[
0
][u
+
1
]
=
z;
}
for
(i
=
0
;i
<
nc;i
++
)
{
cin
>>
ch
>>
u
>>
ch
>>
z;
map[u
+
1
][n
+
1
]
=
z;
}
}
int
BFS()
{
int
i,k;
queue
<
int
>
Q;
memset(tmp,
0
,
sizeof
(tmp));
memset(pre,
0
,
sizeof
(pre));
tmp[s]
=
INF;
Q.push(s);
while
(
!
Q.empty())
{
k
=
Q.front();
Q.pop();
for
(i
=
0
;i
<=
t;i
++
)
{
if
(tmp[i]
==
0
&&
map[k][i])
{
tmp[i]
=
tmp[k]
>
map[k][i]
?
map[k][i]:tmp[k];
pre[i]
=
k;
Q.push(i);
}
}
}
if
(tmp[t]
==
0
)
return
-
1
;
return
1
;
}
void
Edmonds_Karp()
{
int
i,ans
=
0
;
s
=
0
,t
=
n
+
1
;
while
(BFS()
!=
-
1
)
{
ans
+=
tmp[t];
for
(i
=
t;i
!=
s;i
=
pre[i])
{
map[pre[i]][i]
-=
tmp[t];
map[i][pre[i]]
+=
tmp[t];
}
}
cout
<<
ans
<<
endl;
}
int
main()
{
while
(cin
>>
n)
{
Init();
Edmonds_Karp();
}
return
1
;
}