cp1.cpp

// CPP program to find number of subarrays having
// sum in the range L to R.
#include <bits/stdc++.h>
using namespace std;

// Function to find number of subarrays having
// sum less than or equal to x.
int countSub(int arr[], int n, int x)
{

	// Starting index of sliding window.
	int st = 0;

	// Ending index of sliding window.
	int end = 0;

	// Sum of elements currently present
	// in sliding window.
	int sum = 0;

	// To store required number of subarrays.
	int cnt = 0;

	// Increment ending index of sliding
	// window one step at a time.
	while (end < n) {

		// Update sum of sliding window on
		// adding a new element.
		sum += arr[end];

		// Increment starting index of sliding
		// window until sum is greater than x.
		while (st <= end && sum > x) {
			sum -= arr[st];
			st++;
		}

		// Update count of number of subarrays.
		cnt += (end - st + 1);
		end++;
	}

	return cnt;
}

// Function to find number of subarrays having
// sum in the range L to R.
int findSubSumLtoR(int arr[], int n, int L, int R)
{

	// Number of subarrays having sum less
	// than or equal to R.
	int Rcnt = countSub(arr, n, R);

	// Number of subarrays having sum less
	// than or equal to L-1.
	int Lcnt = countSub(arr, n, L - 1);

	return Rcnt - Lcnt;
}

// Driver code.
int main()
{
	int arr[] = { 1, 4, 6 };
	int n = sizeof(arr) / sizeof(arr[0]);

	int L = 3;
	int R = 8;

	cout << findSubSumLtoR(arr, n, L, R);
	return 0;
}