Educational codeforces round 53 (rated for div. 2)

A. diverse substring (prefix and)

Question: Give a string, find a substring that meets the requirements of each letter in the substring to appear no more than the length of the substring/2, the length of the string n <1000.

Question: the starting and ending points of the N-party enumerative substrings. Create a prefix for each letter and you will be able to know the number of each letter in any string.

Code:

#include<iostream>#include<cstdio>#include<cstring>using namespace std;char s[1010];int n;int num[30][1010];int main(){    scanf("%d", &n);    scanf("%s", s+1);    for(int i = 1; i<=n; i++){        for(int k = 0; k<27; k++){            num[k][i] = num[k][i-1];        }        num[s[i]-‘a‘][i] = num[s[i]-‘a‘][i-1]+1;    }    int l = -1, r = -1;    for(int i = 1; i<=n; i++){        for(int j = 1; j<=i; j++){            bool flag = true;            for(int k = 0; k<28; k++){                if(num[k][i]-num[k][j-1]>(i-j+1)/2){                    flag = false;                    break;                }            }            if(flag == true){                l = j; r = i;            }        }    }    if(l!=-1 && r!=-1){        cout<<"YES"<<endl;        for(int i = l; i<=r; i++){            cout<<s[i];        }        cout<<endl;    }    else{        cout<<"NO"<<endl;    }    return 0;}

 

Educational codeforces round 53 (rated for div. 2)