POJ 2396 Budget 上下界网络流 经典题

#include<stdio.h>
#include<string.h>
#define maxn 504
#define maxm 100003
#define inf 1000000000

int min(int a, int b)
{
return a < b ? a : b;
}
int max(int a, int b)
{
return a > b ? a : b;
}

struct E
{
int v, next, c;
}edge[maxm];

int head[maxn], tot;
int n, m;
int S, T;
int s, t;

void init()
{
tot = 0;
memset(head, -1, sizeof(head));
}

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)
{
int i;
for(i = 0; i <= vs; i++)
{
dis[i] = gap[i] = 0;
cur[i] = head[i];
}
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)
{
aug = min(aug, edge[i].c);
pre[v] = u;
cur[u] = i;
u = v;
if(u == t)
{
while(u != s)
{
u = pre[u];
edge[cur[u]].c -= aug;
edge[cur[u]^1].c += aug;
}
maxf += 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 low[maxn][maxn], high[maxn][maxn];
int in[maxn];
bool judge()
{
int i, j;
for(i = head[S]; i != -1; i = edge[i].next)
{
if(edge[i].c && i % 2 == 0)
return 0;
}
return 1;
}

int ans[maxn][maxn];
void solve()
{
int i, j;
for(i = 1; i <= n; i++)
for(j = head[i]; j != -1; j = edge[j].next)
{
int v = edge[j].v;
ans[i][v-n] = edge[j^1].c += low[i][v-n];
}
for(i = 1; i <= n; i++)
{
for(j = 1; j < m; j++)
printf("%d ", ans[i][j]);
printf("%d\n", ans[i][j]);
}
}

int main()
{
int i, j, cas;
int x, y, z;
char buf[11];
scanf("%d", &cas);
while(cas--)
{
scanf("%d%d", &n, &m);
for(i = 0; i <= n; i++)
for(j = 0; j <= m; j++)
low[i][j] = 0, high[i][j] = inf;
init();
s = 0; t = n+m+1; S = t+1; T = S+1;
memset(in, 0, sizeof(in));
for(i = 1; i <= n; i++)
{
scanf("%d", &z);
in[i] += z;
in[s] -= z;
add(s, i, 0);
}
for(i = 1; i <= m; i++)
{
scanf("%d", &z);
in[i+n] -= z;
in[t] += z;
add(i+n, t, 0);
}
int w;
scanf("%d", &w);
bool flag = 1;
while(w--)
{
scanf("%d%d%s%d", &x, &y, buf, &z);
if(!flag) continue;
int a, b, aa, bb;
a = aa = x;
b = bb = y;
if(!x) a = 1, aa = n;
if(!y) b = 1, bb = m;
if(buf[0] == '=')
for(i = a; i <= aa; i++)
for(j = b; j <= bb; j++)
{
if(low[i][j] <= z && high[i][j] >= z)
low[i][j] = high[i][j] = z;
else flag = 0;
}
if(buf[0] == '>')
{
if(z < 0) continue;
for(i = a; i <= aa; i++)
for(j = b; j <= bb; j++)
{
low[i][j] = max(low[i][j], z+1);
if(low[i][j] > high[i][j])
flag = 0;
}
}
if(buf[0] == '<')
{
if(z <= 0) flag = 0;
for(i = a; i <= aa; i++)
for(j = b; j <= bb; j++)
{
high[i][j] = min(high[i][j], z-1);
if(low[i][j] > high[i][j])
flag  = 0;
}
}
}
if(!flag) { printf("IMPOSSIBLE\n"); continue;}
add(t, s, inf);
for(i = 1; i <= n; i++)
for(j = 1; j <= m; j++)
{
in[j+n] += low[i][j];
in[i] -= low[i][j];
add(i, j+n, high[i][j] - low[i][j]);
}
for(i = 0; i <= n+m+1; i++)
{
if(in[i] < 0) add(i, T, -in[i]);
if(in[i] > 0) add(S, i, in[i]);
}
sap(S, T, T+1);
if(!judge())
printf("IMPOSSIBLE\n");
else solve();
if(cas) puts("");
}
return 0;
}