DressEmInVests.java

/*	https://codeforces.com/contest/161/problem/A
#binary-search #greedy #two-pointer
	compare min value of array a and array b.
	max value of array a and array b.
	note: when it's satisfying the condition
*/

import java.util.ArrayList;
import java.util.Scanner;

public class DressEmInVests {

  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    int n = scanner.nextInt();
    int m = scanner.nextInt();
    int x = scanner.nextInt();
    int y = scanner.nextInt();

    int[] a = new int[n + 1];
    for (int i = 1; i < n + 1; i++) {
      int temp = scanner.nextInt();
      a[i] = temp;
    }

    int[] b = new int[m + 1];
    for (int i = 1; i < m + 1; i++) {
      int temp = scanner.nextInt();
      b[i] = temp;
    }

    // result;
    int numPairs = 0;
    ArrayList<String> listResult = new ArrayList<>();
    int i = 1;
    int j = 1;
    while ((i < n + 1) && (j < m + 1)) {
      if (a[i] - x <= b[j] && b[j] <= a[i] + y) {
        listResult.add(i + " " + j);
        i++;
        j++;
        numPairs++;
      } else {
        if (a[i] + y < b[j]) {
          i++;
        } else {
          j++;
        }
      }
    }

    System.out.println(numPairs);
    for (String s : listResult) {
      System.out.println(s);
    }
  }
}