BZOJ2453维护队列&&BZOJ2120数颜色

2016-05-28 11:20:22

共同的思路：维护某种颜色上一次在哪里出现

BZOJ2453 http://www.lydsy.com/JudgeOnline/problem.php?id=2453

BZOJ2120 http://www.lydsy.com/JudgeOnline/problem.php?id=2120

#include<bits/stdc++.h>
#define inf 1000000000
#define ll long long
#define N 10005
#define M 1000005
using namespace std;
int read(){
  int x=0,f=1;char ch=getchar();
  while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
  while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
  return x*f;
}
int block,n,m,q;
int a[N],b[N],c[N],pre[M],pos[N];
char ch[2];
void reset(int x){
  int l=(x-1)*block+1,r=min(x*block,n);
  for(int i=l;i<=r;i++)b[i]=a[i];
  sort(b+l,b+r+1);
}
void update(int x,int v){
  for(int i=1;i<=n;i++)pre[c[i]]=0;
  c[x]=v;
  for(int i=1;i<=n;i++){
    int t=a[i];
    a[i]=pre[c[i]];
    if(t!=a[i])reset(pos[i]);
    pre[c[i]]=i;
  }
}
int find(int x,int v){
  int l=(x-1)*block+1,r=x*block,mid,tmp;
  while(l<=r){
    mid=l+r>>1;
    if(b[mid]<v)tmp=mid,l=mid+1;
    else r=mid-1;
  }
  return tmp-(x-1)*block;
}
int query(int l,int r){
  int ans=0;
  if(pos[l]==pos[r]){
    for(int i=l;i<=r;i++)if(a[i]<l)ans++;
  }
  else{
    for(int i=l;i<=block*pos[l];i++)if(a[i]<l)ans++;
    for(int i=(pos[r]-1)*block+1;i<=r;i++)if(a[i]<l)ans++;
  }
  for(int i=pos[l]+1;i<pos[r];i++)ans+=find(i,l);
  return ans;
}
int main(){
  n=read();q=read();
  for(int i=1;i<=n;i++){
    c[i]=read();a[i]=pre[c[i]];
    pre[c[i]]=i;
  }
  block=(int)sqrt(n);
  for(int i=1;i<=n;i++)pos[i]=(i-1)/block+1;
  if(n%block)m=n/block+1;else m=n/block;
  for(int i=1;i<=m;i++)reset(i);
  while(q--){
    scanf("%s",ch);
    int x=read(),y=read();
    if(ch[0]==‘Q‘)printf("%d\n",query(x,y));
    else update(x,y);
  }
  return 0;
}