Segment tree update query

// C program for
// Segment tree update query
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

// Display array elements
void printElement(int arr[], int n)
{
	for (int i = 0; i < n; ++i)
	{
		printf("  %d", arr[i]);
	}
}
// Returns the sum of given range element
int findSum(int *node, int first, int last, 
            int front, int tail, int position)
{
	if (front <= first && tail >= last)
	{
		// Return range element
		return node[position];
	}
	else if (last < front || first > tail)
	{
		// When element is outside the range
		return 0;
	}
	// Find the middle position of given range
	int mid = first + (last - first) / 2;
	//  visiting the left and right subtree
	return findSum(node, first, mid, front, tail, (position *2) + 1) 
      + findSum(node, mid + 1, last, front, tail, (position *2) + 2);
}
// Handles the request of finding sum of given range element
void nodeSum(int *node, int n, int front, int tail)
{
	if (front < 0 || tail > n - 1 || front > tail)
	{
		// Invalid range
		return;
	}
	else
	{
		int result = findSum(node, 0, n - 1, front, tail, 0);
		printf("\n Given range (%d, %d)", front, tail);
		printf("\n Sum  : %d", result);
	}
}
// Perform update operation
void updateElement(int *node, int front, int tail, 
                   int position, int difference, int current)
{
	if (position < front || position > tail)
	{
		// When position is outside the range
		return;
	}
	// Update new value
	node[current] = node[current] + difference;
	if (front < tail)
	{
		// Find middle node
		int mid = front + (tail - front) / 2;
		// Visit left subtree
		updateElement(node, front, mid, position, difference, 2 *current + 1);
		// Visit right subtree
		updateElement(node, mid + 1, tail, position, difference, 2 *current + 2);
	}
}
// Handles the request to update new element at given position
void updateRequest(int arr[], int n, int *node, int position, int data)
{
	if (position < 0 || position >= n)
	{
		printf("\n Position are not valid \n");
	}
	else
	{
		// Display given data and position
		printf("\n\n Update %d at position %d \n", data, position);
		if (arr[position] == data)
		{
			// When update value is similar
			return;
		}
		else
		{
			// Get difference
			int difference = data - arr[position];
			// Set new value          
			arr[position] = data;
			// Perform tree update
			updateElement(node, 0, n - 1, position, difference, 0);
		}
	}
}
// Assign tree node value
int constructTree(int arr[], int front, int tail, int *node, int position)
{
	if (front == tail)
	{
		// When front and tail are similar, then set new position value
		node[position] = arr[front];
		return node[position];
	}
	// Find middle node
	int mid = front + (tail - front) / 2;
	//  visiting the left and right subtree and set new position value using recursion
	node[position] = constructTree(arr, front, mid, node, (position *2) + 1) 
      + constructTree(arr, mid + 1, tail, node, (position *2) + 2);
	return node[position];
}
// This function are allocating the memory of segment tree
// And return segment tree
int *makeTree(int arr[], int n)
{
	// Calculate height of tree
	int x = (int)(ceil(log2(n)));
	// Get the size of tree
	int max_size = 2 *(int) pow(2, x) - 1;
	// Allocate tree node memory
	int *node = (int *) malloc(sizeof(int) *max_size);
	// Assign the element values
	constructTree(arr, 0, n - 1, node, 0);
	return node;
}
int main(int argc, char
	const *argv[])
{
	int arr[] = {
		2 , 5 , 1 , 9 , 4 , 8 , 7 , 1
	};
	int n = sizeof(arr) / sizeof(arr[0]);
	int *node = makeTree(arr, n);
	printElement(arr, n);
	// Sum query A
	// front = 2, tail = 7
	nodeSum(node, n, 2, 7);
	// Sum query B
	// front = 0, tail = 3
	nodeSum(node, n, 0, 3);
	// Update info
	int data = 4;
	int position = 5;
	// Perform update operation 
	// Test
	updateRequest(arr, n, node, position, data);
	// Sum query C
	// front = 2, tail = 7
	nodeSum(node, n, 2, 7);
	// Sum query D
	// front = 0, tail = 3
	nodeSum(node, n, 0, 3);
	return 0;
}

Output

  2  5  1  9  4  8  7  1
 Given range (2, 7)
 Sum  : 30
 Given range (0, 3)
 Sum  : 17

 Update 4 at position 5

 Given range (2, 7)
 Sum  : 26
 Given range (0, 3)
 Sum  : 17