codeforces 701C They Are Everywhere

问：包含全部种类的连续字符串的最短长度是多少。

写完了才知道写的是双指针。叫two pointer。

以前也写过，今天算是存个档吧~。

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <string>
#include <stack>
#include <queue>

using namespace std;
int s_pos[100100];
int e_pos[100100];
char a[100100];
int kind[200];
int akind[200];
int ak=0;
int ans=0x7f7f7f7f;
int main()
{
    int n;
    scanf ("%d",&n);
    scanf ("%s",a);
    int s_k=0,l=strlen(a);
    s_pos[s_k++]=0;
    for (int i=1; i<l; i++)
    {
        if (a[i]!=a[i-1])
            s_pos[s_k++]=i;
    }
    int e_k=0;
    for (int i=0; i<l-1; i++)
    {
        if (a[i]!=a[i+1])
            e_pos[e_k++]=i;
    }
    e_pos[e_k++]=l-1;
    for (int i=0; i<s_k; i++)
    {
        if (akind[a[s_pos[i]]]==0)
        {
            akind[a[s_pos[i]]]=1;
            ak++;
        }
    }
    if (ak==1)
    {
        printf ("1\n");
        return 0;
    }
    int sp=0,ep=-1,tk=0;
    while (tk!=ak)
    {
        ep++;
        if (kind[a[s_pos[ep]]]==0) tk++;
        kind[a[s_pos[ep]]]++;
    }
    ans=min(ans,s_pos[ep]-e_pos[sp]+1);

    while (sp<s_k&&ep<e_k)
    {
        kind[a[e_pos[sp]]]--;
        sp++;
        if (kind[a[e_pos[sp-1]]]==0)
        {
            tk--;
            while (tk!=ak)
            {
                ep++;
                if (ep==e_k) break;
                if (kind[a[s_pos[ep]]]==0) tk++;
                kind[a[s_pos[ep]]]++;
            }
            if (ep==e_k) break;
            else ans=min(ans,s_pos[ep]-e_pos[sp]+1);
        }
        else
        {
            ans=min(ans,s_pos[ep]-e_pos[sp]+1);
        }
    }
    printf ("%d\n",ans);
    return 0;
}