Cipher

                            Solution in C :

In  C :






#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main() {

   int n, k, i, j, pre, cur, a[1000000];
	char input[2000000];

	scanf("%d", &n);
	scanf("%d", &k);
	scanf("%s", input);

	if (input[0] == '1')
		pre = 1;
	else
	  	pre = 0;

	printf("%d", pre);
	a[0] = pre;
	for (i = 1; i < n; i++) {
		if (input[i] == '1') {
			printf("%d", (pre ^ 1) & 1);
			a[i] = (pre ^ 1) & 1;
		} else {
			printf("%d", (pre ^ 0) & 1);
			a[i] = (pre ^ 0) & 1;
		}
		pre = pre ^ a[i];
		if ((i - k + 2) > 0)
			pre = pre ^ a[i - k + 1];
	}
	printf("\n");    
    return 0;
}
                        

                        Solution in C++ :

In  C++  :






#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int N,K;
    cin>>N>>K;
    char a[N+K-1];
    cin>>a;
    int arr[N],sum=0,i;
    arr[0]=a[0]-48;
    sum=arr[0];
    for(i=1;i<N;i++){
        if(i>=K)sum=(sum-arr[i-K]);   
        if(a[i]=='0') arr[i]=sum%2;
        else arr[i]=(sum+1)%2;
        sum=sum+arr[i];
    }
    
//    arr[N-1]=a[N+K-2]-48;
    for(i=0;i<N;i++)
        cout<<arr[i];
    
    return 0;
}
                    

                        Solution in Java :

In  Java :








import java.io.*;

public class Solution {

    public static void solve(Input in, PrintWriter out) throws IOException {
        int n = in.nextInt();
        int k = in.nextInt();
        char[] c = in.next().toCharArray();
        int x = 0;
        char[] ans = new char[n];
        for (int i = 0; i < n; ++i) {
            ans[i] = (char) (((c[i] - '0') ^ x) + '0');
            x ^= ans[i] - '0';
            if (i >= k - 1) {
                x ^= ans[i - k + 1] - '0';
            }
        }
        out.println(ans);
    }

    public static void main(String[] args) throws IOException {
        PrintWriter out = new PrintWriter(System.out);
        solve(new Input(new BufferedReader(new InputStreamReader(System.in))), out);
        out.close();
    }

    static class Input {
        BufferedReader in;
        StringBuilder sb = new StringBuilder();

        public Input(BufferedReader in) {
            this.in = in;
        }

        public Input(String s) {
            this.in = new BufferedReader(new StringReader(s));
        }

        public String next() throws IOException {
            sb.setLength(0);
            while (true) {
                int c = in.read();
                if (c == -1) {
                    return null;
                }
                if (" \n\r\t".indexOf(c) == -1) {
                    sb.append((char)c);
                    break;
                }
            }
            while (true) {
                int c = in.read();
                if (c == -1 || " \n\r\t".indexOf(c) != -1) {
                    break;
                }
                sb.append((char)c);
            }
            return sb.toString();
        }

        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }

        public long nextLong() throws IOException {
            return Long.parseLong(next());
        }

        public double nextDouble() throws IOException {
            return Double.parseDouble(next());
        }
    }
}
                    

                        Solution in Python : 
                            
In  Python3 :








n, k = map(int, input().split())
s = input()
ans = []
pref = 0
for i in range(n):
    val = pref ^ (ord(s[i]) - ord('0'))
    ans.append(val)
    pref ^= val
    if i >= k - 1:
        pref ^= ans[i - k + 1]
print(''.join(map(str, ans)))