XOR range query

// C program to show segment tree operations like construction, 
// query and update 
#include <stdio.h> 
#include <stdlib.h> 
#include <math.h> 

// A utility function to get the middle index from corner indexes. 
int getMid(int s, int e) { return s + (e -s)/2; } 

/* A recursive function to get the xor of values in given range 
	of the array. The following are parameters for this function. 

	st --> Pointer to segment tree 
	si --> Index of current node in the segment tree. Initially 
			0 is passed as root is always at index 0 
	ss & se --> Starting and ending indexes of the segment 
				represented by current node, i.e., st[si] 
	qs & qe --> Starting and ending indexes of query range */
int getXorUtil(int *st, int ss, int se, int qs, int qe, int si) 
{ 
	// If segment of this node is a part of given range, then return 
	// the xor of the segment 
	if (qs <= ss && qe >= se) 
		return st[si]; 

	// If segment of this node is outside the given range 
	if (se < qs || ss > qe) 
		return 0; 

	// If a part of this segment overlaps with the given range 
	int mid = getMid(ss, se); 
	return getXorUtil(st, ss, mid, qs, qe, 2*si+1) ^ 
		getXorUtil(st, mid+1, se, qs, qe, 2*si+2); 
} 

/* A recursive function to update the nodes which have the given 
index in their range. The following are parameters 
	st, si, ss and se are same as getXorUtil() 
	i --> index of the element to be updated. This index is 
			in input array. 
diff --> Value to be added to all nodes which have i in range */
void updateValueUtil(int *st, int ss, int se, int i, int diff, int si) 
{ 
	// Base Case: If the input index lies outside the range of 
	// this segment 
	if (i < ss || i > se) 
		return; 

	// If the input index is in range of this node, then update 
	// the value of the node and its children 
	st[si] = st[si] + diff; 
	if (se != ss) 
	{ 
		int mid = getMid(ss, se); 
		updateValueUtil(st, ss, mid, i, diff, 2*si + 1); 
		updateValueUtil(st, mid+1, se, i, diff, 2*si + 2); 
	} 
} 

// The function to update a value in input array and segment tree. 
// It uses updateValueUtil() to update the value in segment tree 
void updateValue(int arr[], int *st, int n, int i, int new_val) 
{ 
	// Check for erroneous input index 
	if (i < 0 || i > n-1) 
	{ 
		printf("Invalid Input"); 
		return; 
	} 

	// Get the difference between new value and old value 
	int diff = new_val - arr[i]; 

	// Update the value in array 
	arr[i] = new_val; 

	// Update the values of nodes in segment tree 
	updateValueUtil(st, 0, n-1, i, diff, 0); 
} 

// Return xor of elements in range from index qs (quey start) 
// to qe (query end). It mainly uses getXorUtil() 
int getXor(int *st, int n, int qs, int qe) 
{ 
	// Check for erroneous input values 
	if (qs < 0 || qe > n-1 || qs > qe) 
	{ 
		printf("Invalid Input"); 
		return -1; 
	} 

	return getXorUtil(st, 0, n-1, qs, qe, 0); 
} 

// A recursive function that constructs Segment Tree for array[ss..se]. 
// si is index of current node in segment tree st 
int constructSTUtil(int arr[], int ss, int se, int *st, int si) 
{ 
	// If there is one element in array, store it in current node of 
	// segment tree and return 
	if (ss == se) 
	{ 
		st[si] = arr[ss]; 
		return arr[ss]; 
	} 

	// If there are more than one elements, then recur for left and 
	// right subtrees and store the xor of values in this node 
	int mid = getMid(ss, se); 
	st[si] = constructSTUtil(arr, ss, mid, st, si*2+1) ^ 
			constructSTUtil(arr, mid+1, se, st, si*2+2); 
	return st[si]; 
} 

/* Function to construct segment tree from given array. This function 
allocates memory for segment tree and calls constructSTUtil() to 
fill the allocated memory */
int *constructST(int arr[], int n) 
{ 
	// Allocate memory for segment tree 

	//Height of segment tree 
	int x = (int)(ceil(log2(n))); 

	//Maximum size of segment tree 
	int max_size = 2*(int)pow(2, x) - 1; 

	// Allocate memory 
	int *st = (int *)malloc(sizeof(int)*max_size); 

	// Fill the allocated memory st 
	constructSTUtil(arr, 0, n-1, st, 0); 

	// Return the constructed segment tree 
	return st; 
} 

// Driver program to test above functions 
int main() 
{ 
	int arr[] = {1, 3, 5, 7, 9, 11}; 
	int n = sizeof(arr)/sizeof(arr[0]); 

	// Build segment tree from given array 
	int *st = constructST(arr, n); 

	// Print xor of values in array from index 1 to 3 
	printf("Xor of values in given range = %d\n", 
			getXor(st, n, 1, 3)); 

	// Update: set arr[1] = 10 and update corresponding 
	// segment tree nodes 
	updateValue(arr, st, n, 1, 10); 

	// Find xor after the value is updated 
	printf("Updated xor of values in given range = %d\n", 
			getXor(st, n, 1, 3)); 
	return 0; 
} 

Updating code with array shared in the tutorial video on Youtube.

#include <iostream>
#include <vector>
using namespace std;
int getMid(int s, int e)
{
	return s + (e - s) / 2;
}

void updateValueUtil(vector<int> &st, int si, int L, int R, int i, int prev_val, int new_val)
{
	if (i < L || i > R)
		return;
	st[si] = (st[si] ^ prev_val) ^ new_val; // xor the previous value to nullify with node before xoring new value
	if (R != L)
	{
		int mid = getMid(L, R);
		updateValueUtil(st, si * 2 + 1, L, mid, i, prev_val, new_val);
		updateValueUtil(st, si * 2 + 2, mid + 1, R, i, prev_val, new_val);
	}
}

void updateValue(vector<int> &arr, vector<int> &st, int n, int i, int new_val)
{
	if (i < 0 || i > n - 1)
	{
		cout << "Invalid input";
		return;
	}
	int temp = arr[i];
	arr[i] = new_val;
	updateValueUtil(st, 0, 0, n - 1, i, temp, new_val);
}

int getXorUtil(vector<int> &st, int L, int R, int sL, int sR, int si)
{
	if (sL <= L && sR >= R)
		return st[si];
	if (R < sL || L > sR)
		return 0;
	int mid = getMid(L, R);
	return getXorUtil(st, L, mid, sL, sR, 2 * si + 1) ^
		getXorUtil(st, mid + 1, R, sL, sR, 2 * si + 2);
}

int getXor(vector<int> &st, int n, int L, int R)
{
	if (L < 0 || R > n - 1 || L > R)
	{
		printf("Invalid Input");
		return -1;
	}
	return getXorUtil(st, 0, n - 1, L, R, 0);
}

int constructSTUtil(vector<int> &st, int si, vector<int> &arr, int L, int R)
{
	if (L == R)
	{
		st[si] = arr[L];
		return arr[L];
	}
	int mid = getMid(L, R);
	st[si] = constructSTUtil(st, si * 2 + 1, arr, L, mid) ^
		constructSTUtil(st, si * 2 + 2, arr, mid + 1, R);
	return st[si];
}

int getMaxSize(int n)
{
	int x = (int)(ceil(log2(n)));
	return 2 * (int)pow(2, x) - 1;
}

vector<int> constructST(vector<int> &arr)
{
	int max_size = getMaxSize(arr.size());
	vector<int> st(max_size, 0);
	constructSTUtil(st, 0, arr, 0, arr.size() - 1);
	return st;
}

void printSegmentTree(vector<int> st, int max_size)
{
	for (int i = 0; i < max_size; i++)
	{
		cout << st[i] << " ";
	}
	cout << endl;
}

int main()
{
	vector<int> arr{ 8,5,3,7,6 };
	vector<int> st = constructST(arr);
	printSegmentTree(st, getMaxSize(arr.size()));
	cout << "Xor of values in given range = " << getXor(st, arr.size(), 2, 4) << endl;

	updateValue(arr, st, arr.size(), 3, 11);
	printSegmentTree(st, getMaxSize(arr.size()));
	cout << "Updated xor of given range = " << getXor(st, arr.size(), 2, 4) << endl;

	updateValue(arr, st, arr.size(), 3, 7);
	printSegmentTree(st, getMaxSize(arr.size()));
	cout << "Updated xor of given range = " << getXor(st, arr.size(), 2, 4) << endl;
	return 0;
}