POJ 3469 Dual Core CPU 最小割入门题

#include<stdio.h>
#include<string.h>

const int maxn = 20100;
const int maxm = 200200;
const int inf = 1<<29;

struct node
{
int v, c, next;
}edge[maxm*6];

int head[maxn], tot;
int n, m;

void init()
{
int i;
for(i = 0; i <= n+2; i++)
head[i] = -1;
tot = 0;
}

void add(int s, int t, int c)
{
edge[tot].v = t;
edge[tot].c = c;
edge[tot].next = head[s];
head[s] = tot++;
edge[tot].v = s;
edge[tot].c = 0;
edge[tot].next = head[t];
head[t] = tot++;
}

int gap[maxn], dis[maxn], cur[maxn], pre[maxn];
int sap(int s, int t, int vs)
{
bool flag;
int i;
for(i = 0; i <= vs; i++)
{
cur[i] = head[i];
gap[i] = dis[i] = 0;
}
gap[0] = vs;
int u = pre[s] = s, maxf = 0, aug = inf, v;
while(dis[s] < vs)
{
loop:    for(i = cur[u]; i != -1; i = edge[i].next)
{
v = edge[i].v;
if(edge[i].c > 0 && dis[u] == dis[v] + 1)
{
flag = 1;
if(edge[i].c < aug) aug = edge[i].c;
pre[v] = u;
cur[u] = i;
u = v;
if(u == t)
{
maxf += aug;
while(u != s)
{
u = pre[u];
edge[cur[u]].c -= aug;
edge[cur[u]^1].c += aug;
}
aug = inf;
}
goto loop;
}
}
int min_d = vs;
for(i = head[u]; i != -1; i = edge[i].next)
{
v = edge[i].v;
if(edge[i].c > 0 && dis[v] < min_d)
{
min_d = dis[v];
cur[u] = i;
}
}
if(!(--gap[dis[u]])) break;
++gap[dis[u] = min_d + 1];
u = pre[u];
}
return maxf;
}

int main()
{
int i, j;
int x, y, z;
scanf("%d%d", &n, &m);
init();
int S = 0, T = n+1;
for(i = 1; i <= n; i++)
{
scanf("%d%d", &x, &y);
add(S, i, x);
add(i, T, y);
}
for(i = 1; i <= m; i++)
{
scanf("%d%d%d", &x, &y, &z);
add(x, y, z);
add(y, x, z);
}
printf("%d\n", sap(S, T, n+2));
return 0;
}