Replace all occurrences of pi with 3.14 in a given string

Given a string, the task is to replace all occurrences of pi with 3.14 in the given string.

Examples:

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

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach 1:

Create an empty output string.
Traverse the string from the 0th index till second last index since length of pi is 2.
If the alphabets at the current and (current+1)^th index form the word “pi”, append “3.14” to the output string.
Else append the alphabet at the current index.

Below is the implementation of the above approach:

C++

// 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

// 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 

Python3

# 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#

// 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 

Output:

2 * 3.14 + 3 * 3.14 = 5 * 3.14

Time Complexity: O(N), where N is the length of the given string.

Approach 2: (In Java)
To replace all the PI occurrences to 3.14, use replaceAll() method of 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); 
    } 
} 

Output:

2 * 3.14 + 3 * 3.14 = 5 * 3.14

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

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