- C++ Programming Examples
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- C++ Sum of n Natural Numbers
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- C++ Find Simple Interest
- C++ Fahrenheit to Celsius
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- C++ Print Prime Numbers
- C++ Reverse a Number
- C++ Swap Two Numbers
- C++ Print Multiplication Table
- C++ Find Factorial of Number
- C++ Find Factors of Number
- C++ Find HCF & LCM
- C++ Make Calculator
- C++ Count Digits in Number
- C++ Sum of First & Last Digit
- C++ Product of Digits of Number
- 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
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- C++ Check Leap Year or Not
- Check Reverse equal Original
- C++ Check Perfect Number
- C++ Check Palindrome or Not
- C++ Check Armstrong or Not
- C++ Divisibility Test
- C++ Find Wage of Labor
- C++ Find Discounted Price
- C++ Find Shipping Charge
- C++ Find Telephone Bills
- C++ Calculate Student Grade
- C++ Largest of Two Numbers
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- C++ Number Conversion
- C++ Decimal to Binary
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- C++ Binary to Hexadecimal
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- C++ Octal to Binary
- C++ Octal to Hexadecimal
- C++ Hexadecimal to Decimal
- C++ Hexadecimal to Binary
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- C++ Pattern Programs
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- C++ Array Programs
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- C++ Sum of All Elements
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- C++ Element on Even Position
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- C++ Print Even Numbers in Array
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- C++ Count Even/Odd Numbers
- C++ Sum of Even/Odd Numbers
- C++ Count Positive Negative Zero
- C++ Reverse an Array
- C++ Insert Element in Array
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- C++ Merge two Arrays
- C++ Bubble Sort
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- C++ 2D Array Programs
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- C++ 3D Array Programs
- C++ String Programs
- C++ Print String
- C++ Find Length of String
- C++ Compare Two Strings
- C++ Copy String
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- C++ Reverse a String
- C++ Delete Vowels from String
- C++ Delete Word from String
- C++ Count Character in String
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- C++ Frequency of Word
- C++ Remove Spaces from String
- C++ Sort a String
- C++ Uppercase to Lowercase
- C++ Lowercase to Uppercase
- C++ Swap Two Strings
- C++ Check Anagram or Not
- C++ Capitalize All Words in String
- C++ Capitalize Specific Character
- C++ Get Numbers from String
- C++ File Programs
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- C++ Write Content to File
- C++ Append Data in File
- C++ Read & Display File
- C++ Copy a File
- C++ Merge Two Files
- Count Characters, Words in File
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- C++ List Files in Directory
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- C++ Print ASCII Value
- C++ Add Binary Numbers
- C++ Generate Random Numbers
- C++ Print Smiling Face
- C++ Days into Years, Months
- Add Two Numbers using Pointer
- C++ Print Fibonacci Series
- Generate Armstrong Numbers
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C++ Program to Reverse an Array
In this article, you will learn and get code to reverse an array entered by user at run-time in a C++ program. Here are the list of programs on reversing of an array:
- Print Reverse of an Array without actually Reversing it
- Reverse an Array and then Print
- Reverse an Array using Pointer
- Reverse an Array using User-defined Function
Print Reverse of an Array
This program just prints reverse of an array, without actually reversing it. The question is, write a program in C++ to print reverse of an array. Here is its answer:
#include<iostream> using namespace std; int main() { int arr[10], i; cout<<"Enter 10 Array Elements: "; for(i=0; i<10; i++) cin>>arr[i]; cout<<"\nThe Original Array is:\n"; for(i=0; i<10; i++) cout<<arr[i]<<" "; cout<<"\n\nThe Reverse of Given Array is:\n"; for(i=(10-1); i>=0; i--) cout<<arr[i]<<" "; cout<<endl; return 0; }
This program was build and run under Code::Blocks IDE. Here is its sample run:
Now supply 10 numbers as 10 elements for an array, one by one, to print its reverse as shown in the sample output given below:
When user enters any 10 numbers say 1, 2, 3, ..., 10, then these numbers gets stored in arr[] in following way:
- arr[0]=1
- arr[1]=2
- arr[2]=3
- and so on upto
- arr[9]=10
We've have printed the array from its last index to first, that is its 9th to 0th index to show the reverse of an array as output.
Reverse an Array
This program reverse an array before printing. When the array gets reversed, then when you print the same array, it shows its element in reverse order. This program also allows user to define the size for array.
To reverse an array in C++ programming, you have to ask from user to enter size and then elements (of given size) for the array. Now to reverse, do these things:
- Move element at first index to last, and element at last index to first
- Move element at second index to second last, and element at second last index to second
- and so on
Let's have a look at the program first, its explanation is given later on:
#include<iostream> using namespace std; int main() { int arr[100], tot, i, j, temp; cout<<"Enter the Size for Array: "; cin>>tot; cout<<"Enter "<<tot<<" Array Elements: "; for(i=0; i<tot; i++) cin>>arr[i]; cout<<"\nThe Original Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; j = tot-1; for(i=0; i<j; i++, j--) { temp = arr[i]; arr[i] = arr[j]; arr[j] = temp; } cout<<"\n\nThe Reverse of Given Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; cout<<endl; return 0; }
Here is its sample run, with following user input:
- 5 as size
- 1, 2, 3, 4, 5 as five array elements
After supplying exactly these inputs, press ENTER
key to reverse the array and print both original
and its reverse as shown in the snapshot given below:
The dry run of above C++ program with same user input (as provided in previous output) goes like:
- Initial value, tot=5. Since I've already told about storing of array elements. So arr[0]=1, arr[1]=2, arr[2]=3, arr[3]=4, and arr[4]=5
- Now the original array gets printed using for loop
- After printing the original array, tot-1 or 5-1 or 4 gets initialized to j. So j=4
- Now 0 gets initialized to i and the condition i<j or 0<4 evaluates to be true, therefore program flow goes inside the loop
- And arr[i] or arr[0] or 1 gets initialized to temp. Then arr[j] or arr[4] or 5 gets initialized to arr[i] or arr[0]. And finally temp or 1 gets initialized to arr[j] or arr[4]
- A normal swap operation gets performed with three lines of code. Now arr[0]=5 and arr[4]=1. As you can see, element at last index (4th index) gets moved to first index (0th index), and element at first (0th) index gets moved to last (4th) index
- Now program flow goes to update part of for loop and the value of i gets incremented, whereas the value of j gets decremented. So i=1 and j=3
- And then the condition again gets evaluated. Because the condition i<j or 1<3 evaluates to be true again, therefore program flow goes inside the loop again
- This process continues until the condition evaluates to be false
- In this way, the array gets reversed. So print the array using another for loop to show the reverse of given array
Reverse an Array using Pointers
Now let's reverse an array using pointer. We've created total of three programs using pointer, to reverse an array given by user. This program uses pointer everywhere, from printing to reversing of an array:
#include<iostream> using namespace std; int main() { int arr[100], tot, i, arrTemp[100], *ptr; cout<<"Enter the Size for Array: "; cin>>tot; cout<<"Enter "<<tot<<" Array Elements: "; for(i=0; i<tot; i++) cin>>arr[i]; ptr = &arr[0]; cout<<"\nThe Original Array is:\n"; for(i=0; i<tot; i++) { cout<<*ptr<<" "; ptr++; } ptr--; for(i=0; i<tot; i++) { arrTemp[i] = *ptr; ptr--; } ptr = &arrTemp[0]; for(i=0; i<tot; i++) { arr[i] = *ptr; ptr++; } ptr = &arr[0]; cout<<"\n\nThe Reverse of Given Array is:\n"; for(i=0; i<tot; i++) { cout<<*ptr<<" "; ptr++; } cout<<endl; return 0; }
Here is its sample run with user input, 6 as size, and 10, 20, 30, 40, 50, 60 as its six elements:
Note - The * is called as value at operator. Whereas & is called as address of operator.
Note - The ptr++ initializes the address of next index. For example, if ptr holds the address of 0th index of an array arr[], then after executing ptr++, now ptr holds the address of 1st index of the same array arr[].
Here is another program using pointer to reverse an array. In this program, pointer is used only to reverse the array. Printing of orignal and reversed array gets performed in a normal way:
#include<iostream> using namespace std; int main() { int arr[100], tot, i, arrTemp[100], *ptr; cout<<"Enter the Size for Array: "; cin>>tot; cout<<"Enter "<<tot<<" Array Elements: "; for(i=0; i<tot; i++) cin>>arr[i]; cout<<"\nThe Original Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; ptr = &arr[tot-1]; for(i=0; i<tot; i++) { arrTemp[i] = *ptr; ptr--; } ptr = &arrTemp[0]; for(i=0; i<tot; i++) { arr[i] = *ptr; ptr++; } cout<<"\n\nThe Reverse of Given Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; cout<<endl; return 0; }
This program produces the same output as of previous program. Now here is the last program that reverse an array using pointer. This program is created based on swapping operation. This program doesn't use any other array like previous program:
#include<iostream> using namespace std; int main() { int arr[100], tot, i, j, temp, *ptrOne, *ptrTwo; cout<<"Enter the Size for Array: "; cin>>tot; cout<<"Enter "<<tot<<" Array Elements: "; for(i=0; i<tot; i++) cin>>arr[i]; cout<<"\nThe Original Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; ptrOne = &arr[0]; ptrTwo = &arr[tot-1]; j = tot-1; for(i=0; i<j; i++, j--) { temp = *ptrOne; *ptrOne = *ptrTwo; *ptrTwo = temp; ptrOne++; ptrTwo--; } cout<<"\n\nThe Reverse of Given Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; cout<<endl; return 0; }
Reverse an Array using Function
This is the last program of this article. This program is created using a user-defined function revArray() to reverse an array entered by user. The function takes two arguments. The first argument is array, whereas second argument is its size
#include<iostream> using namespace std; void revArray(int [], int); int main() { int arr[100], tot, i, j, temp; cout<<"Enter the Size for Array: "; cin>>tot; cout<<"Enter "<<tot<<" Array Elements: "; for(i=0; i<tot; i++) cin>>arr[i]; cout<<"\nThe Original Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; revArray(arr, tot); cout<<"\n\nThe Reverse of Given Array is:\n"; for(i=0; i<tot; i++) cout<<arr[i]<<" "; cout<<endl; return 0; } void revArray(int a[], int t) { int i, j, temp; j = t-1; for(i=0; i<j; i++, j--) { temp = a[i]; a[i] = a[j]; a[j] = temp; } }
This program does exactly the same job as of previous program.
Same Program in Other Languages
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