I am new to data structures and algo, and unable to find error in my code for the question
Range Minimum Query
Given an array A of size N, there are two types of queries on this array.
- q l r: In this query you need to print the minimum in the sub-array A[l:r].
- u x y: In this query you need to update A[x]=y.
Input: First line of the test case contains two integers, N and Q, size of array A and number of queries.
Second line contains N space separated integers, elements of A. Next Q lines contain one of the two queries.
Output:
For each type 1 query, print the minimum element in the sub-array A[l:r].
Constraints:
1 ≤ N,Q,y ≤ 10^5
1 ≤ l,r,x≤N
#include<bits/stdc++.h>
using namespace std;
long a [100001];
//global array to store input
long tree[400004];
//global array to store tree
// FUNCTION TO BUILD SEGMENT TREE //////////
void build(long i,long start,long end) //i = tree node
{
if(start==end)
{
tree[i]=a[start];
return;
}
long mid=(start+end)/2;
build(i*2,start,mid);
build(i*2+1,mid+1,end);
tree[i] = min(tree[i*2] , tree[i*2+1]);
}
// FUNCTION TO UPDATE SEGMENT TREE //////////
void update (long i,long start,long end,long idx,long val)
//idx = index to be updated
// val = new value to be given at that index
{
if(start==end)
tree[i]=a[idx]=val;
else
{
int mid=(start+end)/2;
if(start <= idx and idx <= mid)
update(i*2,start,mid,idx,val);
else
update(i*2+1,mid+1,end,idx,val);
tree[i] = min(tree[i*2] , tree[i*2+1]);
}
}
// FUNCTION FOR QUERY
long query(long i,long start,long end,long l,long r)
{
if(start>r || end<l || start > end)
return INT_MAX;
else
if(start>=l && end<=r)
return tree[i];
long mid=(start+end)/2;
long ans1 = query(i*2,start,mid,l,r);
long ans2 = query(i*2+1,mid+1,end,l,r);
return min(ans1,ans2);
}
int main()
{
long n,q;
cin>>n>>q;
for(int i=0 ; i<n ; i++)
cin>>a[i];
//for(int i=1 ; i<2*n ; i++) cout<<tree[i]<<" "; cout<<endl;
build(1,0,n-1);
//for(int i=1 ; i<2*n ; i++) cout<<tree[i]<<" "; cout<<endl;
while(q--)
{
long l,r;
char ch;
cin>>ch>>l>>r;
if(ch=='q')
cout<<query(1,0,n-1,l-1,r-1)<<endl;
else
update(1,0,n-1,l,r);
}
return 0;
}
Example :input
5 15
1 5 2 4 3
q 1 5
q 1 3
q 3 5
q 1 5
q 1 2
q 2 4
q 4 5
u 3 1
u 3 100
u 3 6
q 1 5
q 1 5
q 1 2
q 2 4
q 4 5
Expected output:
1
1
2
1
1
2
3
1
1
1
4
3
