- C++ Programming Examples
- C++ Programming Examples
- C++: Hello World
- C++: Get Input
- C++: Print Integer
- C++: Add two numbers
- C++: Add, Sub, Multiply, Div
- C++: Add Digits
- C++: Find Average and Percentage
- C++: Find Arithmetic Mean
- C++: Sum of n Natural Numbers
- C++: Sum of n Numbers
- C++: Square's Area and Perimeter
- C++: Rectangle's Area and Perimeter
- C++: Triangle's Area and Perimeter
- C++: Area and Circumference
- C++: Find Simple Interest
- C++: Fahrenheit to Celsius
- C++: Celsius to Fahrenheit
- C++: Print Prime Numbers
- C++: Reverse a Number
- C++: Swap Two Numbers
- C++: Print Multiplication Table
- C++: Find Factorial of a Number
- C++: Find Factors of a Number
- C++: Find HCF and LCM
- C++: Create a Calculator
- C++: Count Digits in a Number
- C++: First and Last Digit Sum
- C++: Product of Number Digits
- C++: Sum of Squares of Digits
- C++: Interchange Digits of Number
- C++ if-else Programs
- C++: Check Even or Odd
- C++: Check Prime or Not
- C++: Check Alphabet or Not
- C++: Check Vowel or Not
- C++: Check Leap Year or Not
- C++: Check Reverse equals Original
- C++: Check Perfect Number
- C++: Check Palindrome or Not
- C++: Check Armstrong or Not
- C++: Divisibility Test
- C++: Find Labor Wage
- C++: Find Discounted Price
- C++: Find Shipping Charge
- C++: Find Telephone Bills
- C++: Calculate Student Grade
- C++: Largest of Two Numbers
- C++: Largest of Three Numbers
- C++ Number Conversion
- C++: Decimal to Binary
- C++: Decimal to Octal
- C++: Decimal to Hexadecimal
- C++: Binary to Decimal
- C++: Binary to Octal
- C++: Binary to Hexadecimal
- C++: Octal to Decimal
- C++: Octal to Binary
- C++: Octal to Hexadecimal
- C++: Hexadecimal to Decimal
- C++: Hexadecimal to Binary
- C++: Hexadecimal to Octal
- C++ Pattern Programs
- C++: Pattern Programs
- C++: Print Diamond Pattern
- C++: Print Floyd's Triangle
- C++: Print Pascal's Triangle
- C++ Array Programs
- C++: 1D Array Program
- C++: Linear Search
- C++: Binary Search
- C++: Largest Element in an Array
- C++: Smallest Element in an Array
- C++: Find Second Largest Element
- C++: Find Second Smallest Element
- C++: Sum of All Elements
- C++: Multiply All Elements
- C++: Element in Even Position
- C++: Element in Odd Position
- C++: Print Even Numbers in Array
- C++: Print Odd Numbers in Array
- C++: Count Even or Odd Numbers
- C++: Sum of Even or Odd Numbers
- C++: Count Positive, Negative, Zero
- C++: Reverse an Array
- C++: Insert an Element
- C++: Delete an Element
- C++: Merge two Arrays
- C++: Bubble Sort
- C++: Selection Sort
- C++: Insertion Sort
- C++: Common Elements
- C++: 2D Array Programs
- C++: Add Two Matrices
- C++: Subtract Two Matrices
- C++: Transpose Matrix
- C++: Multiply Two Matrices
- C++: 3D Array Programs
- C++ String Programs
- C++: Print String
- C++: Find String Length
- C++: Compare Two Strings
- C++: Copy String
- C++: String Concatenation
- C++: Reverse a String
- C++: Delete Vowels from a String
- C++: Delete a Word from a String
- C++: Count Characters in a String
- C++: Count Words in a String
- C++: Frequency of Words
- C++: Remove Spaces from Strings
- C++: Sort a String
- C++: Uppercase to Lowercase
- C++: Lowercase to Uppercase
- C++: Swap Two Strings
- C++: Check the Anagram or Not
- C++: Capitalize All Words in a String
- C++: Get Numbers from a String
- C++ File Programs
- C++: Read a File
- C++: Write Content to a File
- C++: Append Data to a File
- C++: Read and Display File
- C++: Copy a File
- C++: Merge Two Files
- Count Characters in a File
- C++: Capitalize Every Word
- C++: List Files in Directory
- C++: Delete a File
- C++: Encrypt and Decrypt a File
- C++ Misc Programs
- C++: Print ASCII Value
- C++: Add Binary Numbers
- C++: Generate Random Numbers
- C++: Print a Smiling Face
- C++: Days into Years and Months
- C++: Add Two Numbers using Pointer
- C++: Print Fibonacci Series
- C++: Generate Armstrong Numbers
- C++: Find nCr and nPr
- C++: Get IP Address
- C++: Print Date and Time
- C++: Shutdown and Restart Computer
- C++ Programming Tutorial
- C++ Tutorial
C++ Program to Reverse a String
In this article, you will learn and get code to reverse a string in C++ programming. Here is the list of programs for reversing a string entered by the user at run-time:
- Reverse a string without using a library function
- Reverse a string using a while loop
- Reverse a string using a for loop
Reverse a string without using a library function
To reverse a string in C++ programming, ask the user to enter a string. Then reverse it and print the reversed string as shown in the program given below:
The question is: write a C++ program to reverse a string entered by the user. Here is its answer:
#include<iostream> #include<stdio.h> using namespace std; int main() { char str[200], strTemp[200]; int len, i=0; cout<<"Enter the String: "; gets(str); while(str[i]!='\0') i++; len = i; strTemp[len] = '\0'; len--; i = 0; while(str[i]!='\0') { strTemp[len] = str[i]; i++; len--; } i=0; while(strTemp[i]!='\0') { str[i] = strTemp[i]; i++; } cout<<"\nReverse = "<<str; cout<<endl; return 0; }
This program was built and runs under the Code::Blocks IDE. Here is its sample run:
Now, as input, enter the string "this is fresherearth" and press the ENTER key to reverse it and print its reverse, as shown in the screenshot below:
The following block of code:
while(str[i]!='\0') i++;
is used to find the length of a string. That is, if a string says "this is fresherearth" entered by the user, then it gets stored in str in a way that:
- str[0]=t
- str[1]=h
- str[2]=i
- and so on up until
- str[19]=r
And at the last index, a null-terminated character (\0) automatically gets assigned. So str[20]=\0.
Because the initial value of i is 0, the while loop condition str[i]!='\0' or str[0]!='\0' or t!='\0' evaluates to true, and the value of i is incremented and the condition is evaluated again. This process continues until the condition is evaluated as false. When the condition gets evaluated to be false, then the variable i holds its value of 20, which is the length of the entered string.
The following block of C++ code:
while(str[i]!='\0') { strTemp[len] = str[i]; i++; len--; }
is used to copy the original string (in character-by-character mode) in a way that the character at the first (0th) index of str gets initialized to the last index of strTemp. That is, we copied the original string into strTemp[] in a way that strTemp holds the original string in reverse order.
And using this block of code:
while(strTemp[i]!='\0') { str[i] = strTemp[i]; i++; }
The value of strTemp gets copied to str. Because strTemp holds the original string's value in reverse order, the reverse of the string gets initialized to str in a character-by-character manner. Now print the value of str on the output, which shows the reverse of the entered string.
Reverse a string without using another string
Previous programs can also be made in this manner without the use of any other character array (string) such as strTemp[]:
#include<iostream> #include<stdio.h> using namespace std; int main() { char str[200], ch; int len, i=0, j; cout<<"Enter the String: "; gets(str); while(str[i]!='\0') i++; len = i; i = 0; j = len-1; while(i<j) { ch = str[i]; str[i] = str[j]; str[j] = ch; i++; j--; } cout<<"\nReverse = "<<str; cout<<endl; return 0; }
This program works by moving characters from the 0th index to the last index, and characters from the last index to the 0th index. Again, the character at the second index gets moved to the second last index, and the character at the second last index gets moved to the second index, and so on.
Here the variable i starts from 0, whereas the variable j starts from len-1 (or the last index's value). And the process of moving the characters continues until the value of i becomes equal to or greater than the value of j.
Reverse a string using a while loop
This program reverse a string using a while loop. It is exactly the same program as the previous one, except this program uses the strlen() function of the string.h header file to find the length of a string.
#include<iostream> #include<stdio.h> #include<string.h> using namespace std; int main() { char str[200], ch; int i, j, len; cout<<"Enter the String: "; gets(str); i = 0; len = strlen(str); j = len-1; while(i<j) { ch = str[i]; str[i] = str[j]; str[j] = ch; i++; j--; } cout<<"\nReverse = "<<str; cout<<endl; return 0; }
Reverse a string using a for loop
Now let's create the same program using the for loop. All the programs given here produce the same output:
#include<iostream> #include<stdio.h> #include<string.h> using namespace std; int main() { char str[200], ch; int i, j, len; cout<<"Enter the String: "; gets(str); len = strlen(str); j = len-1; for(i=0; i<j; i++, j--) { ch = str[i]; str[i] = str[j]; str[j] = ch; } cout<<"\nReverse = "<<str; cout<<endl; return 0; }
The same program in different languages
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