Poj 3320 (ruler acquisition + hash)

Question Link: Http://poj.org/problem? Id = 3320

Theme: A book has P pages, and each page has a knowledge point that can be repeated. Ask for at least several consecutive pages to cover all the knowledge points.

Solutions:

The number of unique elements must be counted and the number of repeated elements must be recorded.

It is best to timely report the number of non-duplicates. There is no doubt that hash must be used.

We recommend that you use map, which can be hash or record the number of each key.

 

Concept of ruler acquisition:

① Extend R without stopping, and drop the knowledge points in the Map until the size of the map meets the requirements.

② Update the result.

② The number of keys (A [L ++]) in the map is-1, which is equivalent to removing this page.

If the number of corresponding keys is <= 0, erase should drop the key to prevent misjudgment of MAP: size.

 

#include "cstdio"#include "map"using namespace std;int a[1000005];int main(){    //freopen("in.txt","r",stdin);    int n,s,l=1,r=1,ans=0x3f3f3f3f;    scanf("%d",&n);    map<int,int> Hash,x;    for(int i=1;i<=n;i++)    {        scanf("%d",&a[i]);        Hash[a[i]]++;    }    s=Hash.size();    while(true)    {        while(x.size()<s&&r<=n) x[a[r++]]++;        if(x.size()<s) break;        ans=min(ans,r-l);        x[a[l++]]--;        if(x[a[l-1]]<=0) x.erase(a[l-1]);    }    printf("%d\n",ans);}

 

13593020

Neopenx

3320

Accepted

1520 K

422 Ms

C ++

549b

00:30:01

Poj 3320 (ruler acquisition + hash)