How to revert back to original array after updating it in C lang? like using a temp pointer or any o-CodePudding

//I want to revert array back to original state after 2nd printf statement OR code any other way such that next code a= (*p) operates on origianl array not on Update array.

CODE:

#include <stdio.h>
#include <stdlib.h>

int main(){
    int arr[]={10,20,30,40,50};   
    int *p = arr;    
    int a;

    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);

    a=   *p;
    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);
    
    //I WANT TO RESET ARRAY BACK TO ORIGINAL STATE after this printf statement or any other way such that next code a=   (*p) operates on origianl array not on Update array.
    
    a=   (*p);
    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);  

}

OUTPUT GIVEN:


 arr[0] = 10, arr[1] = 20, a = 32767, *p = 10
 arr[0] = 11, arr[1] = 20, a = 11, *p = 11
 arr[0] = 12, arr[1] = 20, a = 12, *p = 12┌─[user@user]─[~/Documents/vs_code/DS/TEMP]
└──╼ $

OUTPUT EXPECTED:


 arr[0] = 10, arr[1] = 20, a = 32767, *p = 10
 arr[0] = 11, arr[1] = 20, a = 11, *p = 11
 arr[0] = 11, arr[1] = 20, a = 11, *p = 11┌─[user@user]─[~/Documents/vs_code/DS/TEMP]
└──╼ $

CodePudding user response：

Stop writing C code and learn modern C .

You can use std::array, which has value semantics. This allows you to simply copy the array and copy it back later if that is what you want:

#include <cstdio>
#include <cstdlib>
#include <array>

int main(){
    std::array arr{10,20,30,40,50};   
    int *p = &arr[0];   
    int a = 0;

    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);

    std::array arr2 = arr;
    a=   *p;
    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);
    
    //I WANT TO RESET ARRAY BACK TO ORIGINAL STATE after this printf statement or any other way such that next code a=   (*p) operates on origianl array not on Update array.
    arr = arr2;

    a=   (*p);
    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);  

}

Modifying the copy would have been better.

CodePudding user response：

Thanks for logic: @sam-varshavchik

Copy the original array values somewhere else, then copy them back when you're done fiddling with the array.

#include <stdio.h>
#include <stdlib.h>

int main(){
    int arr[]={10,20,30,40,50};   
    int *p = arr;    
    int a;

    int length= sizeof(arr)/sizeof(arr[0]);

    int arr2[length];

    for(int i=0; i<length;i  ){
        arr2[i]= arr[i];
    }


    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);

    a=   *p;
    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);   
    
    p= &arr2;
    a=   (*p);
    printf("\n arr[0] = %d, arr[1] = %d, a = %d, *p = %d", arr[0], arr[1],a , *p);

    
}