[luogu1503][鬼子进村]

题目链接

思路

将哪些村庄已经被摧毁了放到treap里。查询的时候如果当前村庄已经被毁了，那么就可以直接输出0.不然就输出这个村庄的后继-前驱-1。原因显然

代码

#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<cmath>
#include<ctime>
#include<bitset>
#define ls TR[cur].ch[0]
#define rs TR[cur].ch[1]
using namespace std;
typedef long long ll;
const int N = 50100,INF = 60000;
ll read() {
   ll x=0,f=1;char c=getchar();
   while(c<'0'||c>'9') {
      if(c=='-') f=-1;
      c=getchar();
   }
   while(c>='0'&&c<='9') {
      x=x*10+c-'0';
      c=getchar();
   }
   return x*f;
}
int n,m;
struct node {
   int ch[2],val,id;
}TR[N];
void rotate(int &cur,int f) {
   int son = TR[cur].ch[f];
   TR[cur].ch[f] = TR[son].ch[f ^ 1];
   TR[son].ch[f ^ 1] = cur;
   cur = son;
}
int tot;
void insert(int &cur,int val) {
   if(!cur) {
      cur = ++tot;
      TR[cur].val = val;
      TR[cur].id = rand();
      return;
   }
   int d = val > TR[cur].val;
   insert(TR[cur].ch[d],val);
   if(TR[TR[cur].ch[d]].id < TR[cur].id) rotate(cur,d);
}
void del(int &cur,int val) {
   if(!cur) return;
   if(TR[cur].val == val) {
      if(!ls || !rs) {cur = ls + rs;return;}
      int d = TR[ls].id > TR[rs].id;
      rotate(cur,d);
      del(cur,val);
   }
   else del(TR[cur].ch[val > TR[cur].val],val);
}
int pred(int cur,int val) {
   if(!cur) return 0;
   if(val > TR[cur].val) return max(TR[cur].val,pred(rs,val));
   return pred(ls,val);
}
int nex(int cur,int val) {
   if(!cur) return n + 1;
   if(val < TR[cur].val) return min(TR[cur].val,nex(ls,val));
   return nex(rs,val);
}
int sta[N],top;
int bz[N];
int main() {
   n = read(),m = read();
   char c;
   int rt = 0;
   while(m--) {
      cin>>c;
      if(c == 'D') {
         int x = read();
         insert(rt,x);
         sta[++top] = x;
         bz[x] = 1;
      }
      if(c == 'R') del(rt,sta[top--]),bz[sta[top + 1]] = 0;
      if(c == 'Q') {
         int x = read();
         if(bz[x]) { puts("0");continue;}
         int r = nex(rt,x),l = pred(rt,x);
         printf("%d\n",r - l -1);
      }
   }

   return 0;
}

一言

谁看见过风？我和你，都不曾看见过。