Code:
#include iostream
#include stdio.h
#include math.h
#include conio.h
using namespace std;
int getMid(int s, int e)
{
return s + (e - s) / 2;
}
int getSumUtil(int *st, int ss, int se, int qs, int qe, int index)
{
if (qs <= ss && qe >= se)
return st[index];
if (se < qs || ss > qe)
return 0;
int mid = getMid(ss, se);
return getSumUtil(st, ss, mid, qs, qe, 2 * index + 1) + getSumUtil(st, mid + 1, se, qs, qe, 2 * index + 2);
}
void updateValueUtil(int *st, int ss, int se, int i, int diff, int index)
{
if (i < ss || i > se)
return;
st[index] = st[index] + diff;
if (se != ss)
{
int mid = getMid(ss, se);
updateValueUtil(st, ss, mid, i, diff, 2 * index + 1);
updateValueUtil(st, mid+1, se, i, diff, 2 * index + 2);
}
}
void updateValue(int arr[], int *st, int n, int i, int new_val)
{
if (i < 0 || i > n-1)
{
cout<<"Invalid Input";
return;
}
int diff = new_val - arr[i];
arr[i] = new_val;
updateValueUtil(st, 0, n - 1, i, diff, 0);
}
int getSum(int *st, int n, int qs, int qe)
{
if (qs < 0 || qe > n-1 || qs > qe)
{
cout<<"Invalid Input"<
return -1;
}
return getSumUtil(st, 0, n - 1, qs, qe, 0);
}
int constructSTUtil(int arr[], int ss, int se, int *st, int si)
{
if (ss == se)
{
st[si] = arr[ss];
return arr[ss];
}
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];
}
int *constructST(int arr[], int n)
{
int x = (int)(ceil(log2(n)));
int max_size = 2 * (int)pow(2, x) - 1;
int *st = new int[max_size];
constructSTUtil(arr, 0, n - 1, st, 0);
return st;
}
int main()
{
int arr[] = {1, 3, 5, 7, 9, 11};
int n = sizeof(arr) / sizeof(arr[0]);
int *st = constructST(arr, n);
cout<<"Sum of values in given range:"<
updateValue(arr, st, n, 1, 10);
cout<<"Updated sum of values in given range:"<
getch();
}
Output:
Sum of values in given range:15
Updated sum of values in given range:22
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