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C++ Exercises: Count the number of strings with a given length in an array

C++ Basic Algorithm: Exercise-119 with Solution

Write a C++ program to count the number of strings with a given length in a given array of strings.

Test Data:
({"a", "b", "bb", "c", "ccc" }, 1) ->3
({"a", "b", "bb", "c", "ccc" }, 2) ->1
({"a", "b", "bb", "c", "ccc" }, 3) ->1

Sample Solution:

C++ Code :

#include <iostream>

#include<string.h>
using namespace std;
int test(string arr_str[], int len, int arr_length) {
 int ctr = 0;
 //  cout << arr_str[1] << arr_length << "\n";
 for (int i = 0; i < arr_length; i++) {
   if (arr_str[i].size() == len)
     // cout << arr_str[i] << "\n";
     ctr++;
 }
 return ctr;
}
int main() {
 string text[] = {
   "a",
   "b",
   "bb",
   "c",
   "ccc"
 };
 cout << "Original array strings: ";
 int arr_length = sizeof(text) / sizeof(text[0]);
 for (size_t i = 0; i < arr_length; i++) {
   std::cout << text[i] << ' ';
 }
 int len = 1;
 cout << "\n\nNumber of strings with length " << len << " = " << test(text, len, arr_length) << endl;
 len = 2;
 cout << "\nNumber of strings with length " << len << " = " << test(text, len, arr_length) << endl;
 len = 3;
 cout << "\nNumber of strings with length " << len << " = " << test(text, len, arr_length) << endl;
 return 0;
}

Sample Output:

Original array strings: a b bb c ccc 

Number of strings with length 1 = 3

Number of strings with length 2 = 1

Number of strings with length 3 = 1

Flowchart:

Flowchart: Count the number of strings with a given length in an array.

C++ Code Editor:

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Previous: Find the largest average value between the first and second halves of a given array of integers.
Next: New array from an existing array.

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C++ Programming: Tips of the Day

What is the usefulness of `enable_shared_from_this?

It enables you to get a valid shared_ptr instance to this, when all you have is this. Without it, you would have no way of getting a shared_ptr to this, unless you already had one as a member. 

class Y: public enable_shared_from_this
{
public:

    shared_ptr f()
    {
        return shared_from_this();
    }
}

int main()
{
    shared_ptr p(new Y);
    shared_ptr q = p->f();
    assert(p == q);
    assert(!(p < q || q < p)); // p and q must share ownership
}

The method f() returns a valid shared_ptr, even though it had no member instance. Note that you cannot simply do this:

class Y: public enable_shared_from_this
{
public:

    shared_ptr f()
    {
        return shared_ptr(this);
    }
}

The shared pointer that this returned will have a different reference count from the "proper" one, and one of them will end up losing and holding a dangling reference when the object is deleted.

Ref : https://bit.ly/3pwVzzz