bool isSubSum (int arr[], int n, int sum) {
    int curr_sum = arr[0], s = 0;

    for (int e = 1; e <= n; e++) {
        while (curr_sum > sum && s < e-1) {
            curr_sum -= arr[s];
            s++;
        }

        if (curr_sum == sum) {
            return true;
        }

        if (e < n) {
            curr_sum = arr[e];
        }
    }

    return (curr_sum == sum ? true : false);
}

int main() {
    int arr[]{7,8,2,4,5};
    cout<<isSubSum(arr, 5, 9);
    return 0;
}