POJ3241
4865 ワード
半日撮って他の人のコードを見つけた鍋に...
マンハッタンの最小生成木を記念して、理解しにくいわけではありませんが
250行の鶸コード:
マンハッタンの最小生成木を記念して、理解しにくいわけではありませんが
250行の鶸コード:
#include
#include
#include
#include
#include
using namespace std;
const int N = 1e4 + 5;
#define lson rt << 1
#define rson rt << 1 | 1
#define Lson L, mid, lson
#define Rson mid + 1, R, rson
struct node
{
int a, b, id;
bool operator < (const node& x) const
{
if (a == x.a)
return b < x.b;
return a < x.a;
}
node(int a = 0, int b = 0, int id = 0) : a(a), b(b), id(id) {}
}a[N];
int lis[N];
int li_cnt = 0;
int seg[N << 2];
int is[N << 2];
void pushup(int rt)
{
if (seg[lson] < seg[rson])
{
seg[rt] = seg[lson];
is[rt] = is[lson];
}
else
{
seg[rt] = seg[rson];
is[rt] = is[rson];
}
}
int inf = 0x3f3f3f3f;
void build(int L, int R, int rt)
{
if (L == R)
{
is[rt] = -1;
seg[rt] = inf;
return;
}
int mid = (L + R) >> 1;
build(Lson);
build(Rson);
pushup(rt);
is[rt] = -1;
}
void update(int l, int r, int val, int id, int L, int R, int rt)
{
if (L == R)
{
if (val < seg[rt])
{
seg[rt] = val;
is[rt] = id;
}
return;
}
int mid = (L + R) >> 1;
if (l <= mid)
update(l, r, val, id, Lson);
if (r > mid)
update(l, r, val, id, Rson);
pushup(rt);
}
int query(int l, int r, int L, int R, int rt)
{
// printf("on seg , %d %d %d %d
", l, r, L, R);
if (l <= L && r >= R)
return is[rt];
int mid = (L + R) >> 1;
int ans = inf;
int q_id = -1;
if (l <= mid)
{
int ret = query(l, r, Lson);
if (ret != -1 && (q_id == -1 || ans > a[ret].a + a[ret].b))
{
ans = a[ret].a + a[ret].b;
q_id = ret;
}
// printf("lson ret %d
", ret);
}
if (r > mid)
{
int ret = query(l, r, Rson);
if (ret != -1 && (q_id == -1 || ans > a[ret].a + a[ret].b))
{
ans = a[ret].a + a[ret].b;
q_id = ret;
}
// printf("rson ret %d
", ret);
}
return q_id;
}
int tot = 0;
struct Edge
{
int u, v, w;
Edge(int v = 0, int u = 0, int w = 0) : v(v), u(u), w(w) {}
bool operator < (const Edge& e) const
{
return w < e.w;
}
}edge[N * 4];
int head[N];
void add_edge(int u, int v, int w)
{
edge[++tot] = Edge(v, u, w);
}
void get_edge(int n, int li_cnt)
{
for (int i = n; i >= 1; i--)
{
// printf("get edge %d %d
", i, a[i].id);
int tmp = lower_bound(lis, lis + li_cnt, a[i].b - a[i].a) - lis + 1;
int ret = query(tmp, li_cnt, 1, li_cnt, 1);
// printf("ret %d
", ret);
if (ret != -1)
add_edge(a[i].id, a[ret].id, a[ret].a + a[ret].b - a[i].a - a[i].b);
// printf("update %d
", tmp);
update(tmp, tmp, a[i].a + a[i].b, i, 1, li_cnt, 1);
}
}
int fa[N];
int Find(int x)
{
if (x == fa[x])
return x;
return fa[x] = Find(fa[x]);
}
void Merge(int a, int b)
{
a = fa[a], b = fa[b];
if (a == b)
return;
fa[a] = b;
}
bool check(int n)
{
for (int i = 1; i <= n; i++)
{
if (Find(i) != Find(1))
return false;
}
return true;
}
priority_queue pq;
int main()
{
int n, k;
scanf("%d%d", &n, &k);
li_cnt = 0;
for (int i = 1; i <= n; i++)
{
head[i] = 0;
scanf("%d%d", &a[i].a, &a[i].b);
a[i].id = i;
fa[i] = i;
lis[li_cnt++] = a[i].b - a[i].a;
}
sort(lis, lis + li_cnt);
li_cnt = unique(lis, lis + li_cnt) - lis;
sort(a + 1, a + n + 1);
build(1, li_cnt, 1);
//debug
// puts("ljkahsdkj 1");
get_edge(n, li_cnt);
for (int i = 1; i <= n; i++)
swap(a[i].a, a[i].b);
sort(a + 1, a + n + 1);
li_cnt = 0;
for (int i = 1; i <= n; i++)
lis[li_cnt++] = a[i].b - a[i].a;
sort(lis, lis + li_cnt);
li_cnt = unique(lis, lis + li_cnt) - lis;
build(1, li_cnt, 1);
//debug
// puts("jkshdakj 2");
get_edge(n, li_cnt);
li_cnt = 0;
for (int i = 1; i <= n; i++)
{
a[i].b = -a[i].b;
lis[li_cnt++] = a[i].b - a[i].a;
}
sort(lis, lis + li_cnt);
li_cnt = unique(lis, lis + li_cnt) - lis;
sort(a + 1, a + n + 1);
build(1, li_cnt, 1);
//debug
// puts("jahsdjka 3");
get_edge(n, li_cnt);
li_cnt = 0;
for (int i = 1; i <= n; i++)
{
swap(a[i].a, a[i].b);
lis[li_cnt++] = a[i].b - a[i].a;
}
sort(lis, lis + li_cnt);
li_cnt = unique(lis, lis + li_cnt) - lis;
sort(a + 1, a + n + 1);
build(1, li_cnt, 1);
//debug
// puts("asjdh 4");
get_edge(n, li_cnt);
// puts("");
sort(edge + 1, edge + tot + 1);
for (int i = 1; i <= tot; i++)
{
int x = Find(edge[i].u), y = Find(edge[i].v);
// printf("add_edge %d %d %d yes? %d
", edge[i].u, edge[i].v, edge[i].w, x == y);
if (x != y)
{
Merge(x, y);
pq.push(edge[i].w);
if (check(n))
break;
}
}
k -= 1;
while (k--)
pq.pop();
printf("%d
", pq.top());
return 0;
}