Add problem description test case and fix typo (#113)

Author: spring1843

README.md

@@ -103,7 +103,7 @@ Welcome to **Data Structures and Algorithms in Go**! 🎉 This project is design
         * [Permutations](./backtracking/permutations_test.go)
         * [Generate Parentheses](./backtracking/generate_parentheses_test.go)
         * [Phone Letter Combinations](./backtracking/phone_letter_combinations_test.go)
-        * [Maze](./backtracking/maze_test.go),
+        * [Maze](./backtracking/maze_test.go)
         * [Sudoku](./backtracking/sudoku_test.go)
         * [N Queens](./backtracking/n_queens_test.go)
     * [Graphs](./graph/README.md)

strings/longest_substring_test.go

@@ -20,6 +20,7 @@ func TestLongestSubstrings(t *testing.T) {
 		{"a", ""}, // No occurrence of sequence of two characters
 		{"ab", "ab"},
 		{"abcc", "bcc"},
+		{"aabbc", "aabb"},
 		{"ada", "ada"},
 		{"dafff", "afff"},
 		{"assdeeeddfffha", "deeedd"},