Reemplace todas las ocurrencias de pi con 3.14 en una string dada

Dada una string, la tarea es reemplazar todas las ocurrencias de pi con 3.14 en la string dada.
Ejemplos : 
 

Input : str = "2 * pi + 3 * pi = 5 * pi"
Output : 2 * 3.14 + 3 * 3.14 = 5 * 3.14

Input : str = "pippppiiiipi"
Output : 3.14ppp3.14iii3.14

Input : str = "xpix"
Output : x3.14x

Enfoque 1: 
 

1. Cree una string de salida vacía.
2. Atraviese la string desde el índice 0 hasta el penúltimo índice, ya que la longitud de pi es 2. 
3. Si los alfabetos en el índice actual y (actual+1) ^forman la palabra «pi», agregue «3.14» a la string de salida. 
4. De lo contrario, agregue el alfabeto en el índice actual. 
    

A continuación se muestra la implementación del enfoque anterior: 
 

// C++ program to replace all
// pi in a given string with 3.14
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to replace all occurrences
// of pi in a given with 3.14
string replacePi(string input)
{
    string output;
 
    int size = input.length();
 
    // Iterate through second last
    // element of the string
    for (int i = 0; i < size; ++i) {
 
        // If current and current +1 alphabets
        // form the word 'pi'
        // append 3.14 to output
        if (i + 1 < size and input[i] == 'p' and input[i + 1] == 'i') {
            output += "3.14";
            i++;
        }
 
        // Append the current letter
        else {
            output += input[i];
        }
    }
 
    // Return the output string
    return output;
}
 
// Driver Code
int main()
{
    string input = "2 * pi + 3 * pi = 5 * pi";
    cout << replacePi(input);
    return 0;
}

// Java program to replace all
// pi in a given String with 3.14
 
class GFG {
 
    // Function to replace all occurrences
    // of pi in a given with 3.14
    public String replacePi(String input)
    {
        String output = "";
 
        int size = input.length();
 
        // Iterate through second last
        // element of the String
        for (int i = 0; i < size; ++i) {
            // If current and current +1 alphabets
            // form the word 'pi'
            // append 3.14 to output
            if (i + 1 < size && input.charAt(i) == 'p' && input.charAt(i + 1) == 'i') {
                output += "3.14";
                i++;
            }
 
            // Append the current letter
            else {
                output += input.charAt(i);
            }
        }
 
        // Return the output String
        return output;
    }
 
    // Driver Code
    public static void main(String args[])
    {
        GFG g = new GFG();
        String input = "2 * pi + 3 * pi = 5 * pi";
        System.out.println(g.replacePi(input));
    }
}
 
// This code has been contributed by 29AjayKumar

# Python program to replace all
# pi in a given string with 3.14
 
# Function to replace all occurrences
# of pi in a given with 3.14
def replacePi(input):
    output ="";
 
    size = len(input);
 
    # Iterate through second last
    # element of the string
    for i in range(size):
 
        # If current and current + 1 alphabets
        # form the word 'pi'
        # append 3.14 to output
        if (i + 1 < size and input[i] == 'p' and
                            input[i + 1] == 'i'):
            output += "3.14";
            i+= 1;
 
        # Append the current letter
        else:
            output += input[i];
    # Return the output string
    return output;
 
# Driver Code
input = "2 * pi + 3 * pi = 5 * pi";
print(replacePi(input));
 
# This code contributed by PrinciRaj1992

// C# program to replace all
// pi in a given string with 3.14
 
using System;
// Function to replace all occurrences
// of pi in a given with 3.14
class gfg {
    public string replacePi(string input)
    {
        string output = "";
 
        int size = input.Length;
 
        // Iterate through second last
        // element of the string
        for (int i = 0; i < size; ++i) {
            // If current and current +1 alphabets
            // form the word 'pi'
            // append 3.14 to output
            if (i + 1 < size && input[i] == 'p' && input[i + 1] == 'i') {
                output += "3.14";
                i++;
            }
 
            // Append the current letter
            else {
                output += input[i];
            }
        }
 
        // Return the output string
        return output;
    }
}
 
// Driver Code
class geek {
    public static int Main()
    {
        gfg g = new gfg();
        string input = "2 * pi + 3 * pi = 5 * pi";
        Console.WriteLine(g.replacePi(input));
        return 0;
    }
}
// This code is contributed by Soumik

<script>
 
      // JavaScript program to replace all
      // pi in a given string with 3.14
       
      // Function to replace all occurrences
      // of pi in a given with 3.14
      function replacePi(input) {
        var output = "";
 
        var size = input.length;
 
        // Iterate through second last
        // element of the string
        for (var i = 0; i < size; ++i) {
          // If current and current +1 alphabets
          // form the word 'pi'
          // append 3.14 to output
          if (i + 1 < size && input[i] === "p"
          && input[i + 1] === "i")
          {
            output += "3.14";
            i++;
          }
 
          // Append the current letter
          else {
            output += input[i];
          }
        }
 
        // Return the output string
        return output;
      }
 
      // Driver Code
      var input = "2 * pi + 3 * pi = 5 * pi";
      document.write(replacePi(input));
       
</script>

2 * 3.14 + 3 * 3.14 = 5 * 3.14

Complejidad de tiempo : O(N), donde N es la longitud de la string dada.
Enfoque 2: (en Java) 
para reemplazar todas las ocurrencias de PI a 3.14, use el método replaceAll() de Java String Class.
 

public class ReplacePI {
    public static void main(String[] args)
    {
        // Declare a String
        String expression = "2 * pi + 3 * pi = 5 * pi";
 
        // Call replaceAll() method to replace PI to 3.14
        expression = expression.replaceAll("pi", "3.14");
 
        // Print the result
        System.out.println(expression);
    }
}

2 * 3.14 + 3 * 3.14 = 5 * 3.14