Make a perfect right angled triangle by printing characters of given String

Given a string str, the task is to make a perfect right-angled triangle by printing the characters of the string.

Input: str =  “GEEKSFORGEEKS”
Output :
G 
E E 
K S F 
O R G E

not included E K S because they make our triangle imperfect. i.e.

G 
E E 
K S F 
O R G E 
E K S   

Input: str = “PerfectTriangle”
Output: 
P 
e r 
f e c 
t T r i 
a n g l e 

Approach: To solve the problem follow the above idea:

• Find the point or index up to which a perfect triangle can be made.
• After finding that index implements the nested loop till that index.
• Take a pointer that traverses the string and prints the following character.

Below are the steps for the above approach:

• Initialize a variable say n to store the length of the string.
• Initialize two variables x and y, where x will store the number of rows up to which the outer loop will run and y will store the index up to which the string is used.
• Run a loop till x + y ≤ n, update y = y + x, and increment x i.e the number of rows, to find the index up to which a perfect triangle can be made.
• If x + y – 1 != n, reduce the number of rows by 1.
• Initialize a variable say k = 0 to traverse the string.
• Run a nested loop, outer loop from i = 1 to i ≤ x, and inner loop from j = i to j ≤ i, and now print the characters of the string str[k].

Below is the implementation of the above approach:

C++

// C++ code to make a perfect right angled
// triangle from a given string.

#include <bits/stdc++.h>
using namespace std;

// Funtion that prints perfect
// right angled triangle
void printTriangle(string str)
{
    int n = str.length();

    // x is number of rows upto which the
    // outer loop will run y contains the
    // index upto which the string is used.
    int x = 1, y = 1;

    // Loop to determine the point upto
    // which string is used
    while (x + y <= n) {
        y += x;
        x++;
    }

    // Exclude the unwnated row
    if (x + y - 1 != n) {
        x--;
    }

    // To travese the given string
    int k = 0;

    // Nested loop to make the right
    // angled triangle
    for (int i = 1; i <= x; i++) {
        for (int j = 1; j <= i; j++) {
            cout << str[k] << " ";
            k++;
        }
        cout << endl;
    }
}

// Driver Code
int main()
{

    string str = "GEEKSFORGEEKS";

    // Drivers code
    printTriangle(str);
    return 0;
}

Java

// Java code to make a perfect right angled
// triangle from a given string.
import java.util.*;

class GFG {

  // Function that prints perfect
  // right angled triangle
  public static void printTriangle(String str)
  {
    int n = str.length();

    // x is number of rows upto which the
    // outer loop will run y contains the
    // index upto which the string is used.
    int x = 1, y = 1;

    // Loop to determine the point upto
    // which string is used
    while (x + y <= n) {
      y += x;
      x++;
    }

    // Exclude the unwanted row
    if (x + y - 1 != n) {
      x--;
    }

    // To traverse the given string
    int k = 0;

    // Nested loop to make the right
    // angled triangle
    for (int i = 1; i <= x; i++) {
      for (int j = 1; j <= i; j++) {
        System.out.print(str.charAt(k) + " ");
        k++;
      }
      System.out.println();
    }
  }

  // Driver Code
  public static void main(String[] args)
  {

    String str = "GEEKSFORGEEKS";

    // Drivers code
    printTriangle(str);
  }
}

// This code is contributed by prasad264

Python3

# Python code to make a perfect right angled
# triangle from a given string.

# Function that prints perfect
# right angled triangle
def printTriangle(str):
    n = len(str)

    # x is number of rows upto which the
    # outer loop will run y contains the
    # index upto which the string is used.
    x = 1
    y = 1

    # Loop to determine the point upto
    # which string is used
    while x + y <= n:
        y += x
        x += 1

    # Exclude the unwnated row
    if x + y - 1 != n:
        x -= 1

    # To travese the given string
    k = 0

    # Nested loop to make the right
    # angled triangle
    for i in range(1, x + 1):
        for j in range(1, i + 1):
            print(str[k], end=' ')
            k += 1
        print()

# Driver Code
if __name__ == '__main__':
    str = "GEEKSFORGEEKS"
    printTriangle(str)

C#

// C# code to make a perfect right angled triangle from a
// given string.

using System;

public class GFG {

    // Function that prints perfect right angled triangle
    public static void printTriangle(string str)
    {
        int n = str.Length;

        // x is number of rows upto which the outer loop
        // will run y contains the index upto which the
        // string is used.
        int x = 1, y = 1;

        // Loop to determine the point upto which string is
        // used
        while (x + y <= n) {
            y += x;
            x++;
        }

        // Exclude the unwanted row
        if (x + y - 1 != n) {
            x--;
        }

        // To traverse the given string
        int k = 0;

        // Nested loop to make the right angled triangle
        for (int i = 1; i <= x; i++) {
            for (int j = 1; j <= i; j++) {
                Console.Write(str[k] + " ");
                k++;
            }
            Console.WriteLine();
        }
    }

    static public void Main()
    {

        // Code
        string str = "GEEKSFORGEEKS";

        printTriangle(str);
    }
}

// This code is contributed by karthik.

Javascript

// Function that prints perfect
// right angled triangle
function printTriangle(str) {
    let n = str.length;

    // x is number of rows upto which the
    // outer loop will run y contains the
    // index upto which the string is used.
    let x = 1, y = 1;

    // Loop to determine the point upto
    // which string is used
    while (x + y <= n) {
        y += x;
        x++;
    }

    // Exclude the unwnated row
    if (x + y - 1 !== n) {
        x--;
    }

    // To travese the given string
    let k = 0;

    // Nested loop to make the right
    // angled triangle
    for (let i = 1; i <= x; i++) {
        for (let j = 1; j <= i; j++) {
            console.log(str[k] + " ");
            k++;
        }
        console.log("\n");
    }
}

// Driver Code
let str = "GEEKSFORGEEKS";

// Drivers code
printTriangle(str);

Output

G 
E E 
K S F 
O R G E 

Time Complexity: O (x*x), where x is the point up to which the string is used to make the right-angled triangles.
Auxiliary Space: O(1)

Another Approach:

We can solve the problem using string slicing and repetition.

Steps:

Below are the steps for the above approach:

1. First, take the string.
2. Then, iterate over the length of the string using a for loop.
3. In each iteration of the loop:
   • Check if it is possible to print the remaining string in perfect triangle shape.
   • If not possible break the loop.
   • If possible:
     • Slice the input string up to the index j+i+1 form j^th index using the string[j:j+i+1] syntax.
     • Increment j by i+1.
     • Print the repeated substring in a new line using the print() function.

Below is the implementation of the above approach:

C++

#include <iostream>
#include <string>

// Function that prints perfect
// right angled triangle
void printTriangle(std::string str) {
    int j = 0;
    // Iterate over the length of the string and
    // print the substring and its repetition
    for (int i = 0; i < str.length(); i++) {
        // To remove imperfect part
          if (str.length() < (j + i + 1)) {
            break;
        }
        // Print the triangle
        std::cout << str.substr(j, i + 1) << std::endl;
        j += i + 1;
    }
}

// Test case
int main() {
    std::string str = "GEEKSFORGEEKS";
    printTriangle(str);
    return 0;
}

Java

import java.util.*;

public class GFG {

      // Function that prints perfect
    // right angled triangle
    public static void printTriangle(String str) {
        int j = 0;

          // Iterate over the length of the string and
        // print the substring and its repetition
        for (int i = 0; i < str.length(); i++) {

              // To remove imperfect part
              if (str.length() < (j + i + 1)) {
                break;
            }

              // Print the triangle
            System.out.println(str.substring(j, j + i + 1));
            j += i + 1;
        }
    }

      // Test case
    public static void main(String[] args) {
        String str = "GEEKSFORGEEKS";
        printTriangle(str);
    }
}

Python3

# Python code to make a perfect right angled
# triangle from a given string.

# Function that prints perfect
# right angled triangle
def printTriangle(str):
    j = 0
    # Iterate over the length of the string and
    # print the substring and its repetition
    for i in range(len(str)):
        # To remove imperfect part
        if(len(str) < (j+i+1)):
            break
        # Print the triangle
        print(str[j:(j+i+1)])
        j += i+1

# Driver Code
if __name__ == '__main__':
    str = "GEEKSFORGEEKS"
    printTriangle(str)

# This code is contributed by Susobhan Akhuli

C#

using System;

namespace RightAngledTriangle {
class Program {
    // Function that prints perfect
    // right angled triangle
    static void PrintTriangle(string str)
    {
        int j = 0;
        // Iterate over the length of the string and
        // print the substring and its repetition
        for (int i = 0; i < str.Length; i++) {
            // To remove imperfect part
            if (str.Length < (j + i + 1)) {
                break;
            }
            // Print the triangle
            Console.WriteLine(str.Substring(j, i + 1));
            j += i + 1;
        }
    }

    // Test case
    static void Main(string[] args)
    {
        string str = "GEEKSFORGEEKS";
        PrintTriangle(str);
    }
}
}

Javascript

// Function that prints perfect
// right angled triangle
function printTriangle(str) {
    let j = 0;

    // Iterate over the length of the string and
    // print the substring and its repetition
    for (let i = 0; i < str.length; i++) {

        // To remove imperfect part
        if (str.length < (j + i + 1)) {
            break;
        }
        // Print the triangle
        console.log(str.slice(j, j + i + 1));
        j += i + 1;
    }
}

// Test case
const str = "GEEKSFORGEEKS";
printTriangle(str);

Output

G
EE
KSF
ORGE

Time Complexity: O (x*x), where x is the point up to which the string is used to make the right-angled triangles.
Auxiliary Space: O(1)