2020牛客训练营--G.eli和字符串

#include<bits/stdc++.h>
#define long long ll
#define inf 0x3f3f3f3f
#define maxn 100001
using namespace std;

const int mod=1e9+7;

vector<int> a[200001];
int main(){
	int n,k;
	cin>>n>>k;
	string ss;
	cin>>ss;
	if(k == 1){
		cout<<1<<endl;
		return 0; 
	}
	char c;
	for(int i=0;i<n;i++){
		c = ss[i];
		a[c].push_back(i);
	}
	int res = inf;
	for(int i='a';i<='z';i++){
		if(a[i].size()<k) continue;
		for(int j=k-1;j<a[i].size();j++){
		  res = min(res,a[i][j]-a[i][j-(k-1)]+1);
		} 
	}
	if(res == inf)  cout<<-1<<endl;
	else{
		cout<<res<<endl;
	}
} 

#include<bits/stdc++.h>
using namespace std;
int dp[200010][26]={0};     //26个前缀和数组
int main(){
    int n,k,i,j;
    cin>>n>>k;
    string s;
    cin>>s;
    dp[0][s[0]-'a']=1;
    for(i=1;i<n;i++){
        for(j=0;j<26;j++){
            dp[i][j]=dp[i-1][j];
        }
        dp[i][s[i]-'a']++;
    }
    int mi=1e9;
    for(i=0;i<26;i++){
        int temp=0,t2=0;
        if(dp[n-1][i]<k)continue;
        while(temp<n&&dp[temp][i]==0)temp++;
        while(t2<n&&dp[t2][i]<k)t2++;
        mi=min(mi,t2-temp+1);
        for(temp++;temp<n;temp++){
 
            if(s[temp-1]-'a'==i){
                t2++;
                while(t2<n&&s[t2]-'a'!=i)t2++;
                if(t2==n)break;
            }
            mi=min(mi,t2-temp+1);
        }
    }
    if(mi==1e9)cout<<-1;
    else cout<<mi;
}