洛谷1894 [USACO4.2]完美的牛栏The Perfect Stall
原题链接
二分图最大匹配板子。
每个奶牛向它愿意去的牛棚连边,跑二分图最大匹配即可。
这里我用的是匈牙利算法。
#include<cstdio>
#include<cstring>
using namespace std;
const int N = 410;
const int M = N * N;
int fi[N], ne[M], di[M], mtc[N], l;
bool v[N];
inline int re()
{
int x = 0;
char c = getchar();
bool p = 0;
for (; c < '0' || c > '9'; c = getchar())
p |= c == '-';
for (; c >= '0' && c <= '9'; c = getchar())
x = x * 10 + c - '0';
return p ? -x : x;
}
inline void add(int x, int y)
{
di[++l] = y;
ne[l] = fi[x];
fi[x] = l;
}
bool dfs(int x)
{
int i, y;
for (i = fi[x]; i; i = ne[i])
if (!v[y = di[i]])
{
v[y] = 1;
if (!mtc[y] || dfs(mtc[y]))
{
mtc[y] = x;
return true;
}
}
return false;
}
int main()
{
int i, j, n, m, x, s = 0;
n = re();
re();
for (i = 1; i <= n; i++)
{
m = re();
for (j = 1; j <= m; j++)
{
x = re();
add(i, x + n);
}
}
for (i = 1; i <= n; i++)
{
memset(v, 0, sizeof(v));
if (dfs(i))
s++;
}
printf("%d", s);
return 0;
}
posted on 2018-10-17 12:40 Iowa_Battleship 阅读(89) 评论(0) 编辑 收藏 举报