Codeforces Round #354 (Div. 2) C. Vasya and String

The main topic: there is a (a|b) ^n of A and B consisting of a string of length n, allowing to modify the K-bit. The longest number of substrings that can be composed of a or all B are the longest.

Idea, with two queues to save the position of k+1 A and b respectively, the longest substring ending with I is the length of I minus the value of the queue header element.

#include <iostream> #include <cstdio> #include <memory.h> #include <queue>using namespace std; int main (int argc, const char * argv[]) {    char input[1000005];    int n,k,res1;    Queue<int> Posa;    Queue<int> POSB;    scanf ("%d%d", &n,&k);    for (int i=1;i<=n;i++) {        cin>>input[i];    }    Posa.push (0);//Pre-save 0 position, the actual input subscript starting from 1    posb.push (0);    res1=0;    for (int i=1;i<=n;i++) {        if (input[i]== ' a ') {            posa.push (i);            if (Posa.size () >k+1)                Posa.pop ();        }        else{            Posb.push (i);            if (Posb.size () >k+1)                Posb.pop ();        }        Res1=max (Res1,i-posb.front ());        Res1=max (Res1,i-posa.front ());    }    printf ("%d", res1);    return 0;}

Codeforces Round #354 (Div. 2) C. Vasya and String