Cdoj 1256 Hao Hao Love sports pretreatment/prefix and

Hao Hao Love sports

Time Limit:20 Sec

Memory limit:256 MB

Topic Connection

http://acm.uestc.edu.cn/#/problem/show/1256

Description

Hao Hao likes sports

He N days will participate in < Span id= "mathjax-span-188" class= "math" > m A [1, M integer representation)

Roommate has a Q question

Asked Hao Hao Day to the R Day to participate in how many different kinds of sports

Input

Enter two numbersN,M(1≤n≤< Span id= "mathjax-span-219" class= "mn" >2000 ,   1 ≤m≤ 100 );

Enter N number < Span id= "mathjax-span-230" class= "math" >ai indicates that the first day Hao Hao made the ai type of motion;

Enter a number q(1≤q≤6);

InputQLine two numbers per linel ,   r (1≤l≤< Span id= "mathjax-span-267" class= "Mi" >r≤ n );

Output

Altogether Q Line

Each line output a number indicating Hao Hao in the first Day to the R days altogether how many kinds of activities

Sample Input

5 31 2 3 2 231 42 41 5

Sample Output

323

HINT

Test instructions

Exercises

There are two kinds of positive solutions

1.n^2 pretreatment

Since n is only 2000, we can n^2 to preprocess the answer, and then for each inquiry we are O (1) answer
Core code:
for (i=0;i<n;i++) {
memset (F,0,sizeof (f));
x=0;
for (j=i;j<n;j++) {
if (F[a[j]]==0) {f[a[j]]=1; x + +;}
Ans[i][j]=x;
}
}

2. Prefixes and ideas
We are going to maintain sum[i][j], which shows how many times J has appeared in [1,i].
Then for each inquiry, we just sweep the M, Judge Sum[r][i]-sum[l-1][i] is more than 0 is good
The complexity of this preprocessing is O (n), and the complexity of each query is O (m)
So the overall complexity is O (N+QM)

Code:

#include <cstdio>#include<iostream>#include<algorithm>#include<cstring>using namespacestd;intn,m,i,tmp,j,q,l,r,ans,a[2005][ the];intMain () {scanf ("%d%d",&n,&m);  for(i=1; i<=n;++i) {scanf ("%d",&tmp); A[I][TMP]=1;  for(j=1; j<=m;++j) a[i][j]+=a[i-1][j]; } scanf ("%d",&p);  for(i=1; i<=q;++i) {scanf ("%d%d",&l,&R); Ans=0;  for(j=1; j<=m;++j) ans+= (a[r][j]>a[l-1][j]); printf ("%d\n", ans); }    return 0;}

Cdoj 1256 Hao Hao Love sports pretreatment/prefix and