LYDSY 1412
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 = 10010, maxm = 100005, inf = 0x3f3f3f3f;
int head[maxn], next[maxm], to[maxm], cap[maxm], ecnt, cnt, a[110][110];
int num[maxn], dis[maxn], fa[maxn], que[maxm], cur[maxn];
int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};
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 flow = 0;
int h = 0, t = 0, x;
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 = 0x3f3f3f3f;
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] && dis[to[i]] == dis[x] - 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);
int S = 0, T = n * m + 1;
cnt = T + 1;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
{
scanf("%d", &a[i][j]);
if (a[i][j] == 1)
addEdge(S, (i - 1) * m + j, inf);
if (a[i][j] == 2)
addEdge((i - 1) * m + j, T, inf);
}
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
{
for (int k = 0; k < 4; k++)
{
int x = i + dx[k], y = j + dy[k];
if (x > n || x < 1 || y > m || y < 1)
continue;
if (a[i][j] == 1)
if (a[i][j] != a[x][y])
addEdge((i - 1) * m + j, (x - 1) * m + y, 1);
if (a[i][j] == 2)
if (a[x][y] == 0)
addEdge((x - 1) * m + y, (i - 1) * m + j, 1);
if (a[i][j] == a[x][y] && a[i][j] == 0)
addEdge((i - 1) * m + j, (x - 1) * m + y, 1);
}
}
printf("%d\n", ISAP(S, T));
return 0;
}