POJ 3189 枚举+最大流

#include <iostream>
#include <algorithm>
#include <cstring>
#include <string>
#include <cstdio>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#define eps 1e-5
#define MAXN 1111
#define MAXM 55555
#define INF 10000007
using namespace std;
struct node
{
int v;    // vtex
int c;    // cacity
int f;   // current f in this arc
int next, r;
}edge[MAXM];
int dist[MAXN], nm[MAXN], src, des, n;
int head[MAXN], e;
void add(int x, int y, int c)
{
edge[e].v = y;
edge[e].c = c;
edge[e].f = 0;
edge[e].r = e + 1;
edge[e].next = head[x];
head[x] = e++;
edge[e].v = x;
edge[e].c = 0;
edge[e].f = 0;
edge[e].r = e - 1;
edge[e].next = head[y];
head[y] = e++;
}
void rev_BFS()
{
int Q[MAXN], h = 0, t = 0;
for(int i = 1; i <= n; ++i)
{
dist[i] = MAXN;
nm[i] = 0;
}
Q[t++] = des;
dist[des] = 0;
nm[0] = 1;
while(h != t)
{
int v = Q[h++];
for(int i = head[v]; i != -1; i = edge[i].next)
{
if(edge[edge[i].r].c == 0 || dist[edge[i].v] < MAXN)continue;
dist[edge[i].v] = dist[v] + 1;
++nm[dist[edge[i].v]];
Q[t++] = edge[i].v;
}
}
}
void init()
{
e = 0;
memset(head, -1, sizeof(head));
}
int maxflow()
{
rev_BFS();
int u;
int total = 0;
int cur[MAXN], rpath[MAXN];
for(int i = 1; i <= n; ++i)cur[i] = head[i];
u = src;
while(dist[src] < n)
{
if(u == des)     // find an augmenting path
{
int tf = INF;
for(int i = src; i != des; i = edge[cur[i]].v)
tf = min(tf, edge[cur[i]].c);
for(int i = src; i != des; i = edge[cur[i]].v)
{
edge[cur[i]].c -= tf;
edge[edge[cur[i]].r].c += tf;
edge[cur[i]].f += tf;
edge[edge[cur[i]].r].f -= tf;
}
total += tf;
u = src;
}
int i;
for(i = cur[u]; i != -1; i = edge[i].next)
if(edge[i].c > 0 && dist[u] == dist[edge[i].v] + 1)break;
if(i != -1)     // find an admissible arc, then Advance
{
cur[u] = i;
rpath[edge[i].v] = edge[i].r;
u = edge[i].v;
}
else        // no admissible arc, then relabel this vtex
{
if(0 == (--nm[dist[u]]))break;    // GAP cut, Important!
cur[u] = head[u];
int mindist = n;
for(int j = head[u]; j != -1; j = edge[j].next)
if(edge[j].c > 0)mindist = min(mindist, dist[edge[j].v]);
dist[u] = mindist + 1;
++nm[dist[u]];
if(u != src)
u = edge[rpath[u]].v;    // Backtrack
}
}
return total;
}
int nt, b;
int val[MAXN][33];
int cc[33];
bool solve(int mid)
{
src = nt + b + 1;
des = nt + b + 2;
n = des;
for(int k = 1; k <= b - mid + 1; k++)
{
init();
for(int i = 1; i <= nt; i++) add(src, i, 1);
for(int i = 1; i <= b; i++) add(nt + i, des, cc[i]);
for(int i = 1; i <= nt; i++)
for(int j = k; j < k + mid; j++)
add(i, val[i][j] + nt, 1);
if(maxflow() == nt) return true;
}
return false;
}
int main()
{
scanf("%d%d", &nt, &b);
for(int i = 1; i <= nt; i++)
for(int j = 1; j <= b; j++)
scanf("%d", &val[i][j]);
for(int i = 1; i <= b; i++) scanf("%d", &cc[i]);
int low = 1, high = b;
int ans = b;
while(low <= high)
{
int mid = (low + high) >> 1;
if(solve(mid))
{
ans = min(ans, mid);
high = mid - 1;
}
else low = mid + 1;
}
printf("%d\n", ans);
return 0;
}