diff --git a/1_longest_substring_with_k_distinct_characters.cpp b/1_longest_substring_with_k_distinct_characters.cpp
index 15b5351..6aef394 100644
--- a/1_longest_substring_with_k_distinct_characters.cpp
+++ b/1_longest_substring_with_k_distinct_characters.cpp
@@ -1,32 +1,98 @@
 /*/ problem source:
  * https://www.geeksforgeeks.org/find-the-longest-substring-with-k-unique-characters-in-a-given-string/
+
+ Possible references include:
+https://stackoverflow.com/a/7304184 - custom delimeter for istream
  */
+#include <fstream>
 #include <iostream>
+#include <istream>
+#include <locale>
 #include <ostream>
+#include <sstream>
+#include <string>
 #include <unordered_map>
 #include <vector>
 
+struct semicolon_is_space : std::ctype<char> {
+  // this struct/class is adapted from: https://stackoverflow.com/a/7304184
+  semicolon_is_space() : std::ctype<char>(get_table()){};
+  static mask const *get_table() {
+    static mask rc[table_size];
+    rc[(int)';'] = std::ctype_base::space;
+    rc[(int)'\n'] = std::ctype_base::space;
+    return &rc[0];
+  };
+};
+class input {
+public:
+  std::string s;
+  unsigned long k;
+  friend std::istream &operator>>(std::istream &in, input &i);
+  friend std::ostream &operator<<(std::ostream &out, const input &i);
+};
+
+std::istream &operator>>(std::istream &in, input &i) {
+  std::getline(in, i.s, '\n'); // An inelegant hack to skip newline character
+  std::getline(in, i.s, ';');
+  in >> i.k;
+  return in;
+}
+
+std::ostream &operator<<(std::ostream &out, const input &i) {
+  out << "String:\n" << i.s << "\nK: " << i.k << std::endl;
+  return out;
+}
+
 class result {
 public:
   unsigned long longest_start = 0;
   unsigned long longest_end = 0;
   bool match_found = false;
-  bool operator==(const result r) {
-    return longest_start == r.longest_start && longest_end == r.longest_end &&
-           match_found == r.match_found;
-  };
+  bool operator==(const result r);
+  friend std::istream &operator>>(std::istream &in, result &r);
+  friend std::ostream &operator<<(std::ostream &out, const result &r);
 };
 
-struct input {
-  std::string s;
-  unsigned long k;
-};
+bool result::operator==(const result r) {
+  return longest_start == r.longest_start && longest_end == r.longest_end &&
+         match_found == r.match_found;
+}
+
+std::istream &operator>>(std::istream &in, result &r) {
+  in >> r.longest_start >> r.longest_end >> r.match_found;
+  return in;
+}
+
+std::ostream &operator<<(std::ostream &out, const result &r) {
+  out << "longest_start: " << r.longest_start
+      << " longest_end: " << r.longest_end << " match_found: ";
+  if (r.match_found)
+    out << "true";
+  else
+    out << "false";
+  out << std::endl;
+  return out;
+}
 
-struct test_case {
+class test_case {
+public:
   input i;
   result r;
+  friend std::istream &operator>>(std::istream &in, test_case &t);
+  friend std::ostream &operator<<(std::ostream &out, const test_case &t);
 };
 
+std::istream &operator>>(std::istream &in, test_case &t) {
+  in >> t.i >> t.r;
+  return in;
+}
+
+std::ostream &operator<<(std::ostream &out, const test_case &t) {
+  out << t.i << t.r;
+  return out;
+}
+
 result find(const std::string &s, const unsigned long k) {
   result r;
   std::unordered_map<char, unsigned long> char_count;
@@ -58,11 +124,24 @@ result find(const std::string &s, const unsigned long k) {
   return r;
 }
 
-int main() {
-  std::vector<test_case> test_cases = {{{"aabacbebebe", 3}, {4, 10, true}},
-                                       {{"aabbcc", 1}, {0, 1, true}},
-                                       {{"aabbcc", 3}, {0, 5, true}},
-                                       {{"aaabbb", 3}, {0, 0, false}}};
+int main(int argc, char *argv[]) {
+  std::vector<test_case> test_cases;
+  semicolon_is_space delimeter;
+  for (int i = 1; i < argc; i++) {
+    test_case t;
+    std::ifstream f(argv[i]);
+    f.imbue(std::locale(f.getloc(), new semicolon_is_space));
+    while (f.good()) {
+      f >> t;
+      if (t.i.s.length()) { // skip empty line/string inputs
+        std::cout << t;
+        test_cases.push_back(t);
+      }
+    }
+  }
+
+  std::cout << "\n===================================\n" << std::endl;
+
   for (const test_case &t : test_cases) {
     if (find(t.i.s, t.i.k) == t.r) {
       std::cout << "Test case with string \"" << t.i.s << "\" and k=" << t.i.k
diff --git a/1_longest_substring_with_k_distinct_characters_test_cases.csv b/1_longest_substring_with_k_distinct_characters_test_cases.csv
new file mode 100644
index 0000000..43b86dd
--- /dev/null
+++ b/1_longest_substring_with_k_distinct_characters_test_cases.csv
@@ -0,0 +1,4 @@
+aabacbebebe;3;4;10;1
+aabbcc;1;0;1;1
+aabbcc;3;0;5;1
+aaabbb;3;0;0;0