【BZOJ1018】[SHOI2008]堵塞的交通
【BZOJ1018】[SHOI2008]堵塞的交通
题面
洛谷
题解
菊队讲要用线段树维护连通性，但是好像没人写
解法一
将所有的加边删边离线，然后以最近删除时间为边权，$LCT$维护最大生成树即可
代码
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <map>
using namespace std;
inline int gi() {
register int data = 0, w = 1;
register char ch = 0;
while (!isdigit(ch) && ch != '-') ch = getchar();
if (ch == '-') w = -1, ch = getchar();
while (isdigit(ch)) data = 10 * data + ch - '0', ch = getchar();
return w * data;
}
const int MAX_N = 100005;
const int INF = 1e9;
struct Node { int fa, ch[2], v, d; bool rev; } t[MAX_N << 2];
int stk[MAX_N << 2], top;
void pushup(int x) {
t[x].d = x;
if (t[t[x].d].v > t[t[t[x].ch[0]].d].v) t[x].d = t[t[x].ch[0]].d;
if (t[t[x].d].v > t[t[t[x].ch[1]].d].v) t[x].d = t[t[x].ch[1]].d;
}
void pushrev(int x) {
t[x].rev ^= 1;
swap(t[x].ch[0], t[x].ch[1]);
}
void pushdown(int x) {
if (!t[x].rev) return ;
if (t[x].ch[0]) pushrev(t[x].ch[0]);
if (t[x].ch[1]) pushrev(t[x].ch[1]);
t[x].rev = 0;
}
int get(int x) { return t[t[x].fa].ch[1] == x; }
bool isroot(int x) { return (t[t[x].fa].ch[1] != x) && (t[t[x].fa].ch[0] != x); }
void rotate(int x) {
int k = get(x), y = t[x].fa, z = t[y].fa;
if (!isroot(y)) t[z].ch[get(y)] = x;
t[x].fa = z;
t[t[x].ch[k ^ 1]].fa = y, t[y].ch[k] = t[x].ch[k ^ 1];
t[x].ch[k ^ 1] = y, t[y].fa = x;
pushup(y), pushup(x);
}
void splay(int x) {
stk[top = 1] = x;
for (int i = x; !isroot(i); i = t[i].fa) stk[++top] = t[i].fa;
for (int i = top; i; i--) pushdown(stk[i]);
while (!isroot(x)) {
int y = t[x].fa;
if (!isroot(y)) (get(x) ^ get(y)) ? rotate(x) : rotate(y);
rotate(x);
}
}
void access(int x) { for (int y = 0; x; y = x, x = t[x].fa) splay(x), t[x].ch[1] = y, pushup(x); }
int findroot(int x) { access(x); splay(x); while (t[x].ch[0]) pushdown(x), x = t[x].ch[0]; return x; }
void makeroot(int x) { access(x); splay(x); pushrev(x); }
void split(int x, int y) { makeroot(x); access(y); splay(y); }
void link(int x, int y) { makeroot(x); t[x].fa = y; }
void cut(int x, int y) { split(x, y); t[y].ch[0] = t[x].fa = 0, pushup(y); }
int N, C, tot;
struct Opt { int t, op, x1, x2, del; } a[MAX_N << 1];
map<pair<int, int>, int> mp;
int main () {
#ifndef ONLINE_JUDGE
freopen("cpp.in", "r", stdin);
freopen("cpp.out", "w", stdout);
#endif
C = gi();
for ( ; ; ) {
char ch[10]; scanf("%s", ch);
if (ch[0] == 'E') break;
int op, r1 = gi() - 1, c1 = gi(), r2 = gi() - 1, c2 = gi(), x1 = r1 * C + c1, x2 = r2 * C + c2;
if (x1 > x2) swap(x1, x2);
if (ch[0] == 'O') op = 0;
if (ch[0] == 'C') op = 1;
if (ch[0] == 'A') op = 2;
++N;
if (op == 0) mp[pair<int, int>(x1, x2)] = N, a[N].del = INF;
if (op == 1) a[mp[pair<int, int>(x1, x2)]].del = N;
a[N].t = N, a[N].op = op, a[N].x1 = x1, a[N].x2 = x2;
}
tot = 2 * C;
for (int i = 0; i <= tot; i++) t[i].v = INF;
for (int i = 1; i <= N; i++) {
int x1 = a[i].x1, x2 = a[i].x2, del = a[i].del;
if (a[i].op == 0) {
if (findroot(x1) == findroot(x2)) {
split(x1, x2); int d = t[x2].d;
if (t[d].v >= del) continue;
else cut(x1, d), cut(x2, d);
t[++tot].v = del;
link(x1, tot), link(x2, tot);
}
else t[++tot].v = del, link(x1, tot), link(x2, tot);
}
if (a[i].op == 1)
if (findroot(x1) == findroot(x2)) {
split(x1, x2);
int d = t[x2].d;
if (t[d].v > a[i].t) continue;
cut(x1, d), cut(x2, d);
}
if (a[i].op == 2) {
if (findroot(x1) == findroot(x2)) puts("Y");
else puts("N");
}
}
return 0;
}
解法二
没打，但是可以参考这篇文章
