add leetcode Verifying an Alien Dictionary (#1205)

* add leetcode Verifying an Alien Dictionary

* updating DIRECTORY.md

* Update 953.c

add blank line at the end

---------

Co-authored-by: github-actions[bot] <github-actions@users.noreply.github.com>
Co-authored-by: David Leal <halfpacho@gmail.com>

leetcode/DIRECTORY.md

@@ -110,6 +110,7 @@
 |  917 | [Reverse Only Letters](https://leetcode.com/problems/reverse-only-letters)                                                                             | [C](./src/917.c)  | Easy       |
 |  931 | [Minimum Falling Path Sum](https://leetcode.com/problems/minimum-falling-path-sum)                                                                     | [C](./src/931.c)  | Medium     |
 |  938 | [Range Sum of BST](https://leetcode.com/problems/range-sum-of-bst)                                                                                     | [C](./src/938.c)  | Easy       |
+|  953 | [Verifying an Alien Dictionary](https://leetcode.com/problems/verifying-an-alien-dictionary)                                                           | [C](./src/953.c)  | Easy       |
 |  965 | [Univalued Binary Tree](https://leetcode.com/problems/univalued-binary-tree)                                                                           | [C](./src/965.c)  | Easy       |
 |  977 | [Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array)                                                                   | [C](./src/977.c)  | Easy       |
 |  979 | [Distribute Coins in Binary Tree](https://leetcode.com/problems/distribute-coins-in-binary-tree)                                                       | [C](./src/979.c)  | Medium     |

leetcode/src/953.c

@@ -0,0 +1,40 @@
+#define min(x, y) (((x) < (y)) ? (x) : (y))
+
+bool isWordLess(char* word1, char* word2, int* charOrder){
+    int word1Length = strlen(word1);
+    int word2Length = strlen(word2);
+    
+    for(int i = 0; i < min(word1Length, word2Length); i++) {
+        int charWordsDiff = (charOrder[word1[i] - 'a'] - charOrder[word2[i] - 'a']);
+
+        if (charWordsDiff < 0){
+            return true;
+        }
+
+        if (charWordsDiff > 0){
+            return false;
+        }
+    }
+    
+    return word1Length <= word2Length;
+}
+
+// Keep array-hashtable of order letters.
+// Runtime: O(n)
+// Space: O(1)
+bool isAlienSorted(char ** words, int wordsSize, char * order){
+    const int lowerCaseLettersNumber = 26;
+    int charorder[lowerCaseLettersNumber];
+
+    for(int i = 0; i < lowerCaseLettersNumber; i++) {
+        charorder[order[i] - 'a'] = i;
+    }
+
+    for(int i = 0; i < wordsSize - 1; i++) {
+        if (!isWordLess(words[i], words[i + 1], charorder)){
+            return false;
+        }
+    }
+
+    return true;
+}