F. Scooby ‘Dooby’ Doo

#include <bits/stdc++.h>

using namespace std;


#define Max 1000005
#define PatM 1005

queue<int> result;
char txt[Max], pat[PatM];

void computeLPSArray(int M, int *lps) {
    int len = 0;  // lenght of the previous longest prefix suffix
    int i;

    lps[0] = 0; // lps[0] is always 0
    i = 1;

    // the loop calculates lps[i] for i = 1 to M-1
    while(i < M) {
        if(pat[i] == pat[len]) {
            len++;
            lps[i] = len;
            i++;
        } else { // (pat[i] != pat[len])
            if( len != 0 ) {
                // This is tricky. Consider the example AAACAAAA and i = 7.
                len = lps[len-1];

                // Also, note that we do not increment i here
            } else { // if (len == 0)
                lps[i] = 0;
                i++;
            }
        }
    }
}

void KMPSearch() {
    int M = strlen(pat);
    int N = strlen(txt);

    // create lps[] that will hold the longest prefix suffix values for pattern
    int *lps = (int *)malloc(sizeof(int)*M);
    int j  = 0;  // index for pat[]

    // Preprocess the pattern (calculate lps[] array)
    computeLPSArray(M, lps);

    int i = 0;  // index for txt[]
    while(i < N) {
        if(pat[j] == txt[i]) {
            j++;
            i++;
        }

        if (j == M) {
            result.push(i - j);
            j = lps[j-1];
        }

        // mismatch after j matches
        else if(pat[j] != txt[i]) {
            // Do not match lps[0..lps[j-1]] characters,
            // they will match anyway
            if(j != 0)
                j = lps[j-1];
            else
                i = i+1;
        }
    }
    free(lps); // to avoid memory leak
}

// Driver program to test above function
int main() {
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
#endif
    int tcase, caseNo = 0, front;
    scanf("%d", &tcase);
    getc(stdin);
    while(tcase--) {
        gets(txt);
        gets(pat);
        KMPSearch();
        printf("Case %d: %d\n", ++caseNo, result.size());
        while(!result.empty()) {
            front = result.front();
            result.pop();
            printf("%d", front);
            if(result.size()) printf(" ");
        }
        putchar('\n');
    }
    return 0;
}