# Print number of odd sum sub-arrays of an array

**Problem:** For a given array of positive or negative integers, find count of sub-arrays whose sum is odd.

**Problem Explanation:** For a given array **a** ={1, -2, 3, 4, -5}, odd sum sub-arrays are {1}, {1, -2}, {1, -2 , 3, 4, -5}, {-2, 3}, {-2, 3, 4}, {3}, {3, 4}, {4, -5}, {-5}. Hence, **output** will be 9.

**Java Implementation**

public int oddSumSubArrays(int arr[]) { int[] count = new int[2]; //count[0] stores count of even sum array, //count[1] stores count of odd sum array int sum = 0; for (int i = 0; i<arr.length; i++) { sum = (sum + arr[i]) % 2; count[Math.abs(sum)]++; } //Total odd sum arrays = Total odd sub arrays obtained from count //+ number of odd even pairs int totalOddSumSubArrayCount =count[1] + (count[1]) * (count[0]); return (totalOddSumSubArrayCount); }

**TimeComplexity: O(n)**

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