feat: add Number of Sub-arrays With Odd Sum (#1139)

* add Number of Sub-arrays With Odd Sum

* Update 1524.c

add new line at the end

* Rename README.md to DIRECTORY.md

* chore: apply suggestions from code review

Co-authored-by: David Leal <halfpacho@gmail.com>

leetcode/DIRECTORY.md

@@ -95,5 +95,6 @@
 | 1184 | [Distance Between Bus Stops](https://leetcode.com/problems/distance-between-bus-stops/)                                         | [C](./src/1184.c) | Easy       |
 | 1189 | [Maximum Number of Balloons](https://leetcode.com/problems/maximum-number-of-balloons/)                                         | [C](./src/1189.c) | Easy       |
 | 1207 | [Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/)                                     | [C](./src/1207.c) | Easy       |
+| 1524 | [Number of Sub-arrays With Odd Sum](https://leetcode.com/problems/number-of-sub-arrays-with-odd-sum/)                           | [C](./src/1524.c) | Medium     |
 | 1752 | [Check if Array Is Sorted and Rotated](https://leetcode.com/problems/check-if-array-is-sorted-and-rotated/)                     | [C](./src/1752.c) | Easy       |
 | 2130 | [Maximum Twin Sum of a Linked List](https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/)                           | [C](./src/2130.c) | Medium     |

leetcode/src/1524.c

@@ -0,0 +1,24 @@
+// Counting whole summ. evens sums number and odd summs number.
+// Runtime: O(n),
+// Space: O(1)
+int numOfSubarrays(int* arr, int arrSize){
+    int result = 0;
+    int curSumm = 0;
+    int currOddSumms = 0;
+    int currEvenSumm = 0;
+    int modulo = 1000000000 + 7;
+
+    for(int i = 0; i < arrSize; i++){
+        curSumm += arr[i];
+        if (curSumm % 2 == 0){
+            currEvenSumm++;
+            result = (result + currOddSumms) % modulo;
+        }
+        else {
+            currOddSumms++;
+            result = (result + 1 + currEvenSumm) % modulo;
+        }
+    }
+
+    return result % modulo;
+}