POJ 2135 fee flow basis

Question: give N vertices and M edges, and ask how many shortest paths are going back and forth from 1 to N, and one edge can only go through once.

You can directly repeat the billing flow. However, you need to pay attention to the initial values in the questions and make several WA contributions.

[Cpp]
# Include <iostream>
# Include <cstdio>
# Include <algorithm>
# Include <string>
# Include <cmath>
# Include <cstring>
# Include <queue>
# Include <set>
# Include <vector>
# Include <stack>
# Include <map>
# Include <iomanip>
# Define PI acos (-1.0)
# Deprecision Max 100005
# Define inf 2000000000 // initially inf = 1 <28 but WA, so note that the initial value is large.
# Define LL (x) (x <1)
# Define RR (x) (x <1 | 1)
# Define REP (I, s, t) for (int I = (s); I <= (t); ++ I)
# Define ll long
# Define mem (a, B) memset (a, B, sizeof ())
# Define mp (a, B) make_pair (a, B)
Using namespace std;
Inline void readint (int & ret)
{
Char c;
Do
{
C = getchar ();
}
While (c <'0' | c> '9 ');
Ret = c-'0 ';
While (c = getchar ()> = '0' & c <= '9 ')
Ret = ret * 10 + (c-'0 ');
}
Int n, m;
Struct kdq
{
Int s, e, l, c, next;
} Ed [2, 1000005];
Int head [10005], num;
Void add (int s, int e, int l, int c)
{
Ed [num]. s = s;
Ed [num]. e = e;
Ed [num]. l = l;
Ed [num]. c = c;
Ed [num]. next = head [s];
Head [s] = num ++;
Ed [num]. s = e;
Ed [num]. e = s;
Ed [num]. l = 0;
Ed [num]. c =-c;
Ed [num]. next = head [e];
Head [e] = num ++;
}
Int S, T;
Void init ()
{
Mem (head,-1 );
Num = 0;
}
Int dis [Max];
Bool vis [Max];
Int qe [Max * 10];
Int pre [Max], path [Max];
Int spfa ()
{
REP (I, 0, T) dis [I] = inf, vis [I] = 0;
Dis [S] = 0;
Vis [S] = 1;
Int h = 0, t = 0;
Qe [h ++] = S;
While (h> t)
{
Int tt = qe [t ++];
Vis [tt] = 0;
For (int I = head [tt]; ~ I; I = ed [I]. next)
{
Int ee = ed [I]. e;
Int l = ed [I]. l;
Int c = ed [I]. c;
If (l> 0 & dis [ee]> dis [tt] + c)
{
Pre [ee] = tt;
Path [ee] = I;
Dis [ee] = dis [tt] + c;
If (! Vis [ee])
{
Vis [ee] = 1;
Qe [h ++] = ee;
}
}
}
}
Return dis [T]! = Inf;
}
Int MFMC ()
{
Int M = 0;
While (spfa ())
{
Int ff = inf;
For (int I = T; I! = S; I = pre [I])
Ff = min (ff, ed [path [I]. l );
For (int I = T; I! = S; I = pre [I])
Ed [path [I]. l-= ff, ed [path [I] ^ 1]. l + = ff;
M + = dis [T] * ff;
}
Return M;
}
Int main ()
{
# Ifndef ONLINE_JUDGE
Freopen ("acm.txt", "r", stdin );
# Endif
Init ();
Readint (n );
Readint (m );
S = 0, T = n + 1;
REP (I, 0, m-1)
{
Int a, B, c;
Readint ();
Readint (B );
Readint (c );
Add (a, B, 1, c );
Add (B, a, 1, c );
}
Add (S, 1, 2, 0 );
Add (n, T, 2, 0 );
Cout <MFMC () <endl;
Return 0;
}

# Include <iostream>
# Include <cstdio>
# Include <algorithm>
# Include <string>
# Include <cmath>
# Include <cstring>
# Include <queue>
# Include <set>
# Include <vector>
# Include <stack>
# Include <map>
# Include <iomanip>
# Define PI acos (-1.0)
# Deprecision Max 100005
# Define inf 2000000000 // initially inf = 1 <28 but WA, so note that the initial value is large.
# Define LL (x) (x <1)
# Define RR (x) (x <1 | 1)
# Define REP (I, s, t) for (int I = (s); I <= (t); ++ I)
# Define ll long
# Define mem (a, B) memset (a, B, sizeof ())
# Define mp (a, B) make_pair (a, B)
Using namespace std;
Inline void readint (int & ret)
{
Char c;
Do
{
C = getchar ();
}
While (c <'0' | c> '9 ');
Ret = c-'0 ';
While (c = getchar ()> = '0' & c <= '9 ')
Ret = ret * 10 + (c-'0 ');
}
Int n, m;
Struct kdq
{
Int s, e, l, c, next;
} Ed [2, 1000005];
Int head [10005], num;
Void add (int s, int e, int l, int c)
{
Ed [num]. s = s;
Ed [num]. e = e;
Ed [num]. l = l;
Ed [num]. c = c;
Ed [num]. next = head [s];
Head [s] = num ++;
Ed [num]. s = e;
Ed [num]. e = s;
Ed [num]. l = 0;
Ed [num]. c =-c;
Ed [num]. next = head [e];
Head [e] = num ++;
}
Int S, T;
Void init ()
{
Mem (head,-1 );
Num = 0;
}
Int dis [Max];
Bool vis [Max];
Int qe [Max * 10];
Int pre [Max], path [Max];
Int spfa ()
{
REP (I, 0, T) dis [I] = inf, vis [I] = 0;
Dis [S] = 0;
Vis [S] = 1;
Int h = 0, t = 0;
Qe [h ++] = S;
While (h> t)
{
Int tt = qe [t ++];
Vis [tt] = 0;
For (int I = head [tt]; ~ I; I = ed [I]. next)
{
Int ee = ed [I]. e;
Int l = ed [I]. l;
Int c = ed [I]. c;
If (l> 0 & dis [ee]> dis [tt] + c)
{
Pre [ee] = tt;
Path [ee] = I;
Dis [ee] = dis [tt] + c;
If (! Vis [ee])
{
Vis [ee] = 1;
Qe [h ++] = ee;
}
}
}
}
Return dis [T]! = Inf;
}
Int MFMC ()
{
Int M = 0;
While (spfa ())
{
Int ff = inf;
For (int I = T; I! = S; I = pre [I])
Ff = min (ff, ed [path [I]. l );
For (int I = T; I! = S; I = pre [I])
Ed [path [I]. l-= ff, ed [path [I] ^ 1]. l + = ff;
M + = dis [T] * ff;
}
Return M;
}
Int main ()
{
# Ifndef ONLINE_JUDGE
Freopen ("acm.txt", "r", stdin );
# Endif
Init ();
Readint (n );
Readint (m );
S = 0, T = n + 1;
REP (I, 0, m-1)
{
Int a, B, c;
Readint ();
Readint (B );
Readint (c );
Add (a, B, 1, c );
Add (B, a, 1, c );
}
Add (S, 1, 2, 0 );
Add (n, T, 2, 0 );
Cout <MFMC () <endl;
Return 0;
}