在给定的字符串中用3.14替换所有出现的pi

给定字符串，任务是将给定字符串所有出现的pi替换为3.14。

例子：

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

方法1：

1. 创建一个空的输出字符串。
2. 因为pi的长度是2，所以从第0个索引开始遍历该字符串，直到倒数第二个索引为止。
3. 如果当前索引和第(current + 1)^个索引处的字母组成单词“ pi”，请在输出字符串附加“ 3.14”。
4. 否则，将字母追加到当前索引处。

下面是上述方法的实现：

C++

// C++ program to replace all
// pi in a given string with 3.14
  
#include 
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

输出：

2 * 3.14 + 3 * 3.14 = 5 * 3.14

时间复杂度：O(N)，其中N是给定字符串的长度。

方法2 ：(在Java)
要将所有PI事件替换为3.14，请使用Java String Class的replaceAll()方法。

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);
    }
}

输出：

2 * 3.14 + 3 * 3.14 = 5 * 3.14