Visualization helpers

• Visualization helper methods
  • 1. Two pointers
  • 2. Sliding Window
  • 3. Binary Search
  • 4. Two dimension Array
  • 5. Print Linked list
  • 6. Print Binary Tree

Visualization helper methods

I have created few helper methods to visualize a data structure during an algorithm.

1. Two pointers

• int[] : Integer Array

// Helper method to visualize two pointers for int[]
private void tpi(int[] s, int l, int r, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);
    for (int i = 0; i < s.length; i++) {
        if (i == l && i == r) {
            System.out.printf("[(%s)]", s[i]);
        } else if (i == l) {
            System.out.printf("(%s)", s[i]);
        } else if (i == r) {
            System.out.printf("[%s]", s[i]);
        } else {
            System.out.print(s[i]);
        }
        System.out.print(" ");
    }
    System.out.printf("| l=%s, r=%s %n", l, r);
}

• char[] : Character Array

// Helper method to visualize two pointers for char[]
private void tpc(char[] s, int l, int r, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);
    for (int i = 0; i < s.length; i++) {
        if (i == l && i == r) {
            System.out.printf("[(%s)]", s[i]);
        } else if (i == l) {
            System.out.printf("(%s)", s[i]);
        } else if (i == r) {
            System.out.printf("[%s]", s[i]);
        } else {
            System.out.print(s[i]);
        }
        System.out.print(" ");
    }
    System.out.printf("| l=%s, r=%s %n", l, r);
}

• String : String

// Helper method to visualize two pointers for String
private void tps(String s, int l, int r, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);
    for (int i = 0; i < s.length(); i++) {
        if (i == l && i == r) {
            System.out.printf("[(%s)]", s.charAt(i));
        } else if (i == l) {
            System.out.printf("(%s)", s.charAt(i));
        } else if (i == r) {
            System.out.printf("[%s]", s.charAt(i));
        } else {
            System.out.print(s.charAt(i));
        }
        System.out.print(" ");
    }
    System.out.printf("| l=%s, r=%s %n", l, r);
}

2. Sliding Window

• int[] : Integer Array

// Helper method to visualize sliding window for int[]
private void swi(int[] nums, int l, int r, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);
    for (int i = 0; i < nums.length; i++) {
        if (i == l) {
            System.out.print("[");
        }
        System.out.print(nums[i]);
        if (i == r) {
            System.out.print("]");
        }
        System.out.print(" ");
    }
    System.out.printf("| l=%s, r=%s %n", l, r);
}

• char[] : Character Array

// Helper method to visualize sliding window for char[]
private void swi(char[] chars, int l, int r, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);
    for (int i = 0; i < chars.length; i++) {
        if (i == l) {
            System.out.print("[");
        }
        System.out.print(chars[i]);
        if (i == r) {
            System.out.print("]");
        }
        System.out.print(" ");
    }
    System.out.printf("| l=%s, r=%s %n", l, r);
}

• String : String

// Helper method to visualize sliding window for String
private void sws(String s, int l, int r, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);
    for (int i = 0; i < s.length(); i++) {
        if (i == l) {
            System.out.print("[");
        }
        System.out.print(s.charAt(i));
        if (i == r) {
            System.out.print("]");
        }
        System.out.print(" ");
    }
    System.out.printf("| l=%s, r=%s %n", l, r);
}

3. Binary Search

// Helper method to visualize binary search (how pointers are moving)
private void pbs(int[] a, int m, int l, int r, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);
    System.out.printf("L: %s, M: %s, R: %s | ", l, m, r);
    for (int i = 0; i < a.length; i++) {
        if (i == m) {
            if (m == l && m == r) {
                System.out.printf("[({%s})]", a[i]);
            } else if (m == l) {
                System.out.printf("({%s})", a[i]);
            } else if (m == r) {
                System.out.printf("[{%s}]", a[i]);
            } else {
                System.out.printf("{%s}", a[i]);
            }
        } else if (i == l && i == r) {
            System.out.printf("[(%s)]", a[i]);
        } else if (i == l) {
            System.out.printf("(%s)", a[i]);
        } else if (i == r) {
            System.out.printf("[%s]", a[i]);
        } else {
            System.out.print(a[i]);
        }
        System.out.print(" ");
    }
    System.out.println();
}

4. Two dimension Array

• int[][] : Integer Array

// Helper method to visualize two dimesional int array int[][]
private void tdi(int[][] a) {
    for (int[] row : a) {
        System.out.println(Arrays.toString(row));
    }
    System.out.println("---");
}

• char[][] : Character Array

// Helper method to visualize two dimesional char array char[][]
private void tdc(char[][] a) {
    for (char[] row : a) {
        System.out.println(Arrays.toString(row));
    }
    System.out.println("---");
}

• String[][] : String

// Helper method to visualize two dimesional String array String[][]
private void tds(String[][] a) {
    for (String[] row : a) {
        System.out.println(Arrays.toString(row));
    }
    System.out.println("---");
}

5. Print Linked list

// Helper method to visualize LinkedList
private void pll(ListNode head, String... prefix) {
    if (prefix.length == 0) {
        prefix = new String[] { "" };
    }
    System.out.print(prefix[0]);

    int size = 0;
    ListNode curr = head;
    while (curr != null) {
        size++;
        curr = curr.next;
    }

    curr = head;
    int i = 0;
    while (curr != null) {
        if (i == size / 2) {
            System.out.printf("[%s] -> ", curr.val);
        } else {
            System.out.printf("%s -> ", curr.val);
        }
        curr = curr.next;
        i++;
    }
    System.out.print("null\n");
}

6. Print Binary Tree

// Helper method to visualize bianry tree
private void pbt(final TreeNode node) {
    String result = ppt(node, new StringBuilder(), true, new StringBuilder());
    System.out.println(result);
}

private String pbtUtil(TreeNode node, StringBuilder prefix, boolean isTail, StringBuilder sb) {
    if (node.right != null) {
      pbtUtil(node.right, new StringBuilder().append(prefix).append(isTail ? "│   " : "    "), false,
          sb);
    }
    sb.append(prefix).append(isTail ? "└── " : "┌── ").append(node.val).append("\n");
    if (node.left != null) {
      pbtUtil(node.left, new StringBuilder().append(prefix).append(isTail ? "    " : "│   "), true, sb);
    }
    return sb.toString();
}