{"post":"

Reverse Only Alphabets Problem

Given: A string containing special characters (!,@,^,&,$) and alphabets (‘a’ to ‘z’ and ‘A’ to ‘Z’). We have to reverse only the alphabets keeping the special symbols intact.

Input: A@%gh,q

Output: q@%hg,A

Explanation: Here we have to reverse characters in the array and ignore the special symbols. Only the position of characters will change and position of special symbols will be same.

# Approach 1(Efficient)

In this method, we will be not using extra space.

Code:

#include <iostream>\n#include <string.h>\n\n// Function returns 1 (true) if x is alphabet, 0 (false) otherwise\nint check_alpha(char z)\n{\n  int flag = 0;\n  if ((z >= 'A' && z <= 'Z') || (z >= 'a' && z <= 'z'))\n    flag = 1;\n  else\n    flag = 0;\n  if (flag == 0)\n    return 0;\n  else\n    return 1;\n}\n\n// Function reverses a string\nvoid revstring(char str[])\n{\n  // Initializing x and y\n  int x = strlen(str) - 1, y = 0;\n  // Traversing from both ends, till x &y are equal\n  while (y < x)\n  {\n    // leave special characters\n    if (!check_alpha(str[y]))\n      y++;\n    else if (!check_alpha(str[x]))\n      x--;\n    else\n    // if both s[y] and s[x] are alphabatical characters\n    // swap the alphabets\n    {\n      char temp;\n      temp = str[y];\n      str[y] = str[x];\n      str[x] = temp;\n      y++;\n      x--;\n    }\n  }\n}\n\nint main()\n{\n  char str[] = \"A@%gh&q\";\n  std::cout << \"Input string: \" << str << std::endl;\n  revstring(str);\n  std::cout << \"Output string: \" << str << std::endl;\n  return 0;\n}\n\n

Output

Input string: A@%gh&q\nOutput string: qhg%@A\n\n

# Approach 2

In this approach, we have to use extra space by making a new array like pass[].

Follow the following steps:-

Create a auxilary character array like pass[].
Now copy alphabets from given array to pass[].
Reversing pass[] using string reversal.
We traverse input string and pass in a single loop. When a alphabet character occurs in input string, replace it with present character of pass[].

Code

#include <iostream>\n#include <string.h>\n\n// Function returns 1 (true) if x is alphabet, 0 (false) otherwise\nint check_alpha(char z)\n{\n  int flag = 0;\n  if ((z >= 'A' && z <= 'Z') || (z >= 'a' && z <= 'z'))\n    flag = 1;\n  else\n    flag = 0;\n  if (flag == 0)\n    return 0;\n  else\n    return 1;\n}\n\n// Function reverses a string\nvoid revstring(char str[])\n{\n  // Initializing x and y\n  int x = strlen(str) - 1, y = 0;\n  // Traversing from both ends, till x &y are equal\n  while (y < x)\n  {\n    char temp;\n    temp = str[y];\n    str[y] = str[x];\n    str[x] = temp;\n    y++;\n    x--;\n  }\n}\n\nint main()\n{\n  char str[] = \"A@%gh&q\";\n  std::cout << \"Input string: \" << str << std::endl;\n\n  // Create a auxiliary character array\n  char pass[strlen(str)];\n  // Copy alphabets from given array to pass[]\n  int k = 0;\n  for (int i = 0; i < strlen(str); i++)\n  {\n    if (check_alpha(str[i]))\n    {\n      pass[k] = str[i];\n      k++;\n    }\n  }\n  // Reverse pass[] using string reversal\n  revstring(pass);\n  // Traverse input string and pass in a single loop\n  // When a alphabet character occurs in input string, \n  // replace it with present character of pass[]\n  k = 0;\n  for (int i = 0; i < strlen(str); i++)\n  {\n    if (check_alpha(str[i]))\n    {\n      str[i] = pass[k];\n      k++;\n    }\n  }\n\n  std::cout << \"Output string: \" << str << std::endl;\n  return 0;\n}\n\n

Output

Input string: A@%gh&q\nOutput string: qhg%@A\n

\n","title":"Reverse Only Alphabets Problem","authorDetails":{"name":"Prabhnoor Maingi","slug":"prabhnoor-maingi"},"description":"Learn how to implement a program in C++ to reverse only the alphabets in a given string. This solution includes step by step instructions and code examples to help you understand the process.","slug":"reverse-only-alphabets-problem/","articleId":"636a83447bb1ce5072622b60","bookmarkStatus":{"isBookmarked":false,"bookmarkId":null}}