Bugs.java

package javaapplication1;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class Bugs {
 
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String line;
 
        int[] stack = new int[2000000];
 
        while ((line = reader.readLine()) != null) {
            String[] split = line.split(" ");
 
            int n = Integer.parseInt(split[0]);
            char[] bug = split[1].toCharArray();
 
            int idx = -1;
            int state = 0;
 
            int c;
            while (n > 0 && (c = reader.read()) != -1) {
                if (c == '\n') {
                    n--;
                }
 
                if (bug[state] == c) {
                    state++;
                    if (state == bug.length) {
                        if (idx >= 0) {
                            state = stack[idx--];
                        } else {
                            state = 0;
                        }
                    }
                } else if (bug[0] == c) {
                    stack[++idx] = state;
                    state = 1;
                } else {
                    if(state > 0) {
                        stack[++idx] = state;
                    }
                    for(int i = 0; i <= idx; i++) {
                        state = stack[i];
                        for (int j = 0; j < state; j++) {
                            System.out.print(bug[j]);
                        }
                    }
                    state = 0;
                    idx = -1;
                    System.out.print((char) c);
                }
            }
        }
    }
}