LYDSY 1934
题目大意
暂无
题目解法
暂无
RTFC
#include <cstdio>
#include <cstring>
inline int min(int a, int b) { return a < b ? a : b; }
const int maxn = 310, maxm = maxn * maxn * 2, inf = 0x3f3f3f3f;
int head[maxn], to[maxm], cap[maxm], next[maxm], ecnt;
int dis[maxn], num[maxn], fa[maxn], que[maxn], cur[maxn], cnt;
inline void addEdge_impl_(int f, int t, int c)
{
next[ecnt] = head[f];
head[f] = ecnt;
to[ecnt] = t;
cap[ecnt] = c;
ecnt++;
}
inline void addEdge(int f, int t, int c)
{
addEdge_impl_(f, t, c);
addEdge_impl_(t, f, 0);
}
int ISAP(int s, int e)
{
int h = 0, t = 0, x, flow = 0;
for (int i = 0; i <= cnt; i++) dis[i] = cnt;
dis[que[t++] = e] = 0;
while (h != t)
for (int i = head[x = que[h++]]; ~i; i = next[i])
if (cap[i ^ 1] > 0 && dis[to[i]] > dis[x] + 1)
dis[que[t++] = to[i]] = dis[x] + 1;
memset(num, 0, sizeof(num));
for (int i = 0; i <= cnt; i++) num[dis[i]]++, cur[i] = head[i];
x = s;
while (dis[s] < cnt)
{
if (x == e)
{
int curFlow = inf;
for (x = e; x != s; x = to[fa[x] ^ 1]) curFlow = min(curFlow, cap[fa[x]]);
for (x = e; x != s; x = to[fa[x] ^ 1]) cap[fa[x]] -= curFlow, cap[fa[x] ^ 1] += curFlow;
flow += curFlow, x = s;
}
bool needRetreat = true;
for (int i = cur[x]; needRetreat && ~i; i = next[i])
if (cap[i] > 0 && dis[x] == dis[to[i]] + 1)
needRetreat = false, cur[x] = i, fa[x = to[i]] = i;
if (needRetreat)
{
int mn = cnt - 1;
for (int i = head[x]; ~i; i = next[i])
if (cap[i]) mn = min(mn, dis[to[i]]);
if (--num[dis[x]] == 0) break;
++num[dis[x] = mn + 1];
cur[x] = head[x];
if (x != s) x = to[fa[x] ^ 1];
}
}
return flow;
}
int main()
{
memset(head, -1, sizeof(head));
int n, m;
scanf("%d%d", &n, &m);
cnt = n + 2;
for (int i = 1, x; i <= n; i++)
{
scanf("%d", &x);
if (x)
addEdge(0, i, 1);
else
addEdge(i, n + 1, 1);
}
for (int i = 1, x, y; i <= m; i++)
{
scanf("%d%d", &x, &y);
addEdge_impl_(x, y, 1);
addEdge_impl_(y, x, 1);
}
printf("%d", ISAP(0, n + 1));
return 0;
}