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 ;

 }

巴特西

CodeForces 221D Little Elephant and Array

Little Elephant and Array

Input

Output

Sample Input

Source

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