feat: add LeetCode problem 118 (#996)

* added 118 to list

* added 118.c

leetcode/README.md

@@ -37,6 +37,7 @@ LeetCode
 |109|[Convert Sorted List to Binary Search Tree](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/) | [C](./src/109.c)|Medium|
 |110|[Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/) | [C](./src/110.c)|Easy|
 |112|[Path Sum](https://leetcode.com/problems/path-sum/) | [C](./src/112.c)|Easy|
+|118|[Pascal's Triangle](https://leetcode.com/problems/pascals-triangle/) | [C](./src/118.c)|Easy|
 |121|[Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/) | [C](./src/121.c)|Easy|
 |125|[Valid Palindrome](https://leetcode.com/problems/valid-palindrome/) | [C](./src/125.c)|Easy|
 |136|[Single Number](https://leetcode.com/problems/single-number/) | [C](./src/136.c)|Easy|

leetcode/src/118.c

@@ -0,0 +1,26 @@
+/**
+ * Return an array of arrays of size *returnSize.
+ * The sizes of the arrays are returned as *returnColumnSizes array.
+ * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
+ */
+int** generate(int numRows, int* returnSize, int** returnColumnSizes){
+    *returnSize = numRows;
+    int **ans = (int**)malloc(numRows*sizeof(int*));
+    *returnColumnSizes = (int*)malloc(numRows*sizeof(int)); 
+   
+   for (int i=0; i<numRows; i++) {
+        (*returnColumnSizes)[i] = i + 1;
+        ans[i] = (int*)malloc((i+1)*sizeof(int));
+    }
+    
+    ans[0][0] = 1;
+    
+    for (int i=1; i<numRows; i++) {
+        ans[i][0] = 1;
+        for (int j=1; j<i; j++) {
+            ans[i][j] = ans[i-1][j-1] + ans[i-1][j];
+        }
+        ans[i][i] = 1;
+    }
+    return ans;
+}