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struct node{ | |
int val; | |
void split(node& l, node& r){} | |
void merge(node& a, node& b) | |
{ | |
val = min( a.val, b.val ); | |
} | |
}tree[1<<(n+1)]; | |
node range_query(int root, int left_most_leaf, int right_most_leaf, int u, int v) | |
{ | |
//query the interval [u,v), ie, {x:u<=x<v} | |
//the interval [left_most_leaf,right_most_leaf) is | |
//the set of all leaves descending from "root" | |
if(u<=left_most_leaf && right_most_leaf<=v) | |
return tree[root]; | |
int mid = (left_most_leaf+right_most_leaf)/2, | |
left_child = root*2, | |
right_child = left_child+1; | |
tree[root].split(tree[left_child], tree[right_child]); | |
node l=identity, r=identity; | |
//identity is an element such that merge(x,identity) = merge(identity,x) = x for all x | |
if(u < mid) l = range_query(left_child, left_most_leaf, mid, u, v); | |
if(v > mid) r = range_query(right_child, mid, right_most_leaf, u, v); | |
tree[root].merge(tree[left_child],tree[right_child]); | |
node n; | |
n.merge(l,r); | |
return n; | |
} | |
void mergeup(int postn) | |
{ | |
postn >>=1; | |
while(postn>0) | |
{ | |
tree[postn].merge(tree[postn*2],tree[postn*2+1]); | |
postn >>=1; | |
} | |
} | |
void update(int pos, node new_val) | |
{ | |
pos+=(1<<n); | |
tree[pos]=new_val; | |
mergeup(pos); | |
} |
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