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