Can I Integrates Two For Loop In One For Loop?

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hello guys ,
first i am beginner programmer and

i have one question...
can i Integrates the for loop in the following code to be """ for(int i=0,j=0;i<a,j<b;++i,++j)

instead of this ???

C++

#include

using namespace std;

int main(){
	
	int n,a,b;
	cin>>n>>a;
	int arr[a];
	for(int i=0;i<a;++i){
		cin>>arr[i];
	}
	cin>>b;
	int arr2[b];
	for(int j=0;j<b;++j){
		cin>>arr2[j];
	}   
	}

Posted 21-Sep-14 3:39am

Member 10680023

Updated 21-Sep-14 3:53am

PIEBALDconsult

v3

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CPallini 24-Sep-14 3:30am

There's no reason for doing that.

3 solutions

Solution 3

No. But if you have multiple input loops like that, you should extract them into a function. That way you don't have to write the same code twice. Also note that there is a mistake in your original code: you cannot define a array using a variable as size - you need to allocate the array dynamically. Also you should check whether the size is in fact a meaningful value:

C++

bool read_array(int*& arr, int& arr_size) {
   bool result = false;
   // get desired array size
   cin >> arr_size;
   // ensure reasonable size, assuming you don't really
   // want to enter more than 100 values manually
   if (arr_size > 0 && arr_size < 100) {
      // allocate array on the heap
      arr = new int[arr_size];
      // read array elements
      for (int index = 0; index < arr_size; ++index) {
         cin >> arr[index];
      }
      result = true;
   }
   return result;
}
int main () {
   int* arr = nullptr; // always initialize
   int a = 0; // initialization not so important here, but make it a habit!
   if (!read_array(arr, a) {
      cout << "Failed to read first array" << endl;
      a = 0; // reset to 0, just to be sure
   }
   int* arr2 = nullptr;
   int b = 0;
   if (!read_array(arr2, b) {
      cout << "Failed to read second array" << endl;
      b = 0; // reset to 0, just to be sure
   }
   return 0;
}

Posted 23-Sep-14 1:45am

Stefan_Lang

Updated 23-Sep-14 20:03pm

v2

Comments

Philippe Mori 23-Sep-14 20:45pm

You code need some small fixes like arr_size variable declared twice and nullpt without final r on arr2 initialization.

Stefan_Lang 24-Sep-14 2:01am

Thanks for the info, I'll fix it.

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OriginalGriff · Accepted Answer · 2014-09-21T03:54:00

Not really, no - the number of iterations (the number of times your go round the loop) is controlled by a different user input - so if he enters two different numbers you would have to have the same loop go round two different numbers of times - which is just silly! :laugh:
It is possible, but it would take more code, be more awkward to read, and harder for the user to work out what he is supposed to be entering.

Leave it as two loops!

PIEBALDconsult · Accepted Answer · 2014-09-21T03:55:00

Solution 2

That should work if the two arrays are the same size, but then you wouldn't need two index variables anyway.

Posted 21-Sep-14 3:55am