CodeForces 221D Little Elephant and Array

Little Elephant and Array

Time Limit: 4000ms

Memory Limit: 262144KB

This problem will be judged on CodeForces. Original ID: 221D
64-bit integer IO format: %I64d      Java class name: (Any)

The Little Elephant loves playing with arrays. He has array a, consisting of n positive integers, indexed from 1 to n. Let's denote the number with index i as ai.

Additionally the Little Elephant has m queries to the array, each query is characterised by a pair of integers lj and rj (1 ≤ lj ≤ rj ≤ n). For each query lj, rj the Little Elephant has to count, how many numbers x exist, such that number x occurs exactly x times among numbers alj, alj + 1, ..., arj.

Help the Little Elephant to count the answers to all queries.

 

Input

The first line contains two space-separated integers n and m (1 ≤ n, m ≤ 105) — the size of array a and the number of queries to it. The next line contains n space-separated positive integers a1, a2, ..., an (1 ≤ ai ≤ 109). Next m lines contain descriptions of queries, one per line. The j-th of these lines contains the description of the j-th query as two space-separated integers lj and rj (1 ≤ lj ≤ rj ≤ n).

 

Output

In m lines print m integers — the answers to the queries. The j-th line should contain the answer to the j-th query.

 

Sample Input

Input

7 2
3 1 2 2 3 3 7
1 7
3 4

Output

3
1

Source

Codeforces Round #136 (Div. 2)

 

解题：线段树，甚妙

改段求点

 #include <bits/stdc++.h>
 #define A first
 #define B second
 using namespace std;
 typedef pair<int,int> pii;
 const int maxn = ;
 int tree[maxn<<];
 inline void pushdown(int v){
     if(tree[v]){
         tree[v<<] += tree[v];
         tree[v<<|] += tree[v];
         tree[v] = ;
     }
 }
 void update(int L,int R,int lt,int rt,int val,int v){
     if(lt <= L && rt >= R){
         tree[v] += val;
         return;
     }
     pushdown(v);
     int mid = (L + R)>>;
     if(lt <= mid) update(L,mid,lt,rt,val,v<<);
     if(rt > mid) update(mid + ,R,lt,rt,val,v<<|);
 }
 int query(int L,int R,int pos,int v){
     if(L == R) return tree[v];
     pushdown(v);
     int mid = (L + R)>>;
     if(pos <= mid) return query(L,mid,pos,v<<);
     if(pos > mid) return query(mid + ,R,pos,v<<|);
 }
 int ans[maxn],a[maxn],cnt[maxn];
 vector<int>pos[maxn];
 struct QU{
     int x,y,id;
     bool operator<(const QU &rhs)const{
         return y < rhs.y;
     }
 }q[maxn];
 pii pre[maxn];
 int main(){
     int n,m;
     while(~scanf("%d%d",&n,&m)){
         memset(tree,,sizeof tree);
         memset(cnt,,sizeof cnt);
         for(int i = ; i < n; ++i)
             scanf("%d",a + i);
         for(int i = ; i < m; ++i){
             scanf("%d%d",&q[i].x,&q[i].y);
             q[i].id = i;
         }
         for(int i = ; i < maxn; ++i) pos[i].clear();
         sort(q,q + m);
         for(int i = , j = ; i < n; ++i){
             if(a[i] <= n){
                 pos[a[i]].push_back(i + );
                 cnt[a[i]]++;
                 if(cnt[a[i]] == a[i]){
                     pre[a[i]] = pii(,pos[a[i]][]);
                     update(,n,pre[a[i]].A,pre[a[i]].B,,);
                 }else if(cnt[a[i]] > a[i]){
                     update(,n,pre[a[i]].A,pre[a[i]].B,-,);
                     pre[a[i]] = pii(pre[a[i]].B + ,pos[a[i]][cnt[a[i]] - a[i]]);
                     update(,n,pre[a[i]].A,pre[a[i]].B,,);
                 }
             }
             while(j < m && q[j].y == i + ){
                 ans[q[j].id] = query(,n,q[j].x,);
                 ++j;
             }
         }
         for(int i = ; i < m; ++i)
             printf("%d\n",max(,ans[i]));
     }
     return ;
 }

改点求段

 #include <bits/stdc++.h>
 #define A first
 #define B second
 using namespace std;
 typedef pair<int,int> pii;
 const int maxn = ;
 int tree[maxn<<];
 void update(int L,int R,int pos,int val,int v){
     if(L == R){
         tree[v] += val;
         return;
     }
     int mid = (L + R)>>;
     if(pos <= mid) update(L,mid,pos,val,v<<);
     if(pos > mid) update(mid + ,R,pos,val,v<<|);
     tree[v] = tree[v<<] + tree[v<<|];
 }
 int query(int L,int R,int lt,int rt,int v){
     if(lt <= L && rt >= R) return tree[v];
     int mid = (L + R)>>,ret = ;
     if(lt <= mid) ret = query(L,mid,lt,rt,v<<);
     if(rt > mid) ret += query(mid + ,R,lt,rt,v<<|);
     return ret;
 }
 int a[maxn],cnt[maxn],ans[maxn];
 vector<int>pos[maxn];
 struct QU{
     int x,y,id;
     bool operator<(const QU &rhs)const{
         return y < rhs.y;
     }
 }q[maxn];
 int main(){
     int n,m;
     while(~scanf("%d%d",&n,&m)){
         memset(tree,,sizeof tree);
         memset(cnt,,sizeof cnt);
         for(int i = ; i < maxn; ++i) pos[i].clear();
         for(int i = ; i < n; ++i)
             scanf("%d",a + i);
         for(int i = ; i < m; ++i){
             scanf("%d%d",&q[i].x,&q[i].y);
             q[i].id = i;
         }
         sort(q,q + m);
         for(int i = ,j = ; i < n; ++i){
             if(a[i] <= n){
                 pos[a[i]].push_back(i + );
                 ++cnt[a[i]];
                 if(cnt[a[i]] >= a[i]) update(,n,pos[a[i]][cnt[a[i]] - a[i]],,);
                 if(cnt[a[i]] >= a[i] + ) update(,n,pos[a[i]][cnt[a[i]] - a[i] - ],-,);
                 if(cnt[a[i]] > a[i] + ) update(,n,pos[a[i]][cnt[a[i]] - a[i] - ],,);
             }
             while(j < m && q[j].y == i + ){
                 ans[q[j].id] = query(,n,q[j].x,q[j].y,);
                 ++j;
             }
         }
         for(int i = ; i < m; ++i)
             printf("%d\n",ans[i]);
     }
     return ;
 }