feat: Project Euler Problem 7 - #167 (#598)

* Please check this solution to Q7 of Project Euler

* rename file

* fix code formatting

* added doc

* updating DIRECTORY.md

* added see-also references

Co-authored-by: adityasheth305 <43900942+adityasheth305@users.noreply.github.com>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

DIRECTORY.md

@@ -324,6 +324,7 @@
     * [Sol](https://github.com/TheAlgorithms/C/blob/master/project_euler/problem_6/sol.c)
   * Problem 7
     * [Sol](https://github.com/TheAlgorithms/C/blob/master/project_euler/problem_7/sol.c)
+    * [Sol2](https://github.com/TheAlgorithms/C/blob/master/project_euler/problem_7/sol2.c)
   * Problem 8
     * [Sol1](https://github.com/TheAlgorithms/C/blob/master/project_euler/problem_8/sol1.c)
     * [Sol2](https://github.com/TheAlgorithms/C/blob/master/project_euler/problem_8/sol2.c)

project_euler/problem_7/sol.c

@@ -1,11 +1,14 @@
 /**
  * \file
- * \brief [Problem 7](https://projecteuler.net/problem=7) solution
+ * \brief [Problem 7](https://projecteuler.net/problem=7) solution.
+ * @see Another version: problem_7/sol2.c
  */
 #include <stdio.h>
 #include <stdlib.h>
 
-/** Main function */
+/** Main function
+ * @return 0 on exit
+ */
 int main(void)
 {
     char *sieve;

project_euler/problem_7/sol2.c

@@ -0,0 +1,38 @@
+/**
+ * \file
+ * \brief [Problem 7](https://projecteuler.net/problem=7) solution.
+ * @see Faster version problem_7/sol.c
+ */
+#include <stdio.h>
+
+/** Main function
+ * @return 0 on exit
+ */
+int main()
+{
+    int n;
+    scanf("%d", &n);
+    int number_of_prime = 0;
+    for (int i = 2;; i++)
+    {
+        int divisors = 0;
+        for (int j = 1; j <= i; j++)
+        {
+            if (i % j == 0)
+            {
+                divisors++;
+            }
+        }
+        if (divisors == 2)
+        {
+            number_of_prime++;
+            if (number_of_prime == n)
+            {
+                printf("%d", i);
+                break;
+            }
+        }
+    }
+
+    return 0;
+}