## Solución al problema número BRCKTS de Spoj - BRCKTS.

Cualquier duda no dudes en contactar.

``````#include <bits/stdc++.h>
using namespace std;
#define INF 0x3F3F3F3F

struct node {
long long int pa;
long long int pc;
};
node join(node left,node right)
{
node res;
int n = min(left.pa, right.pc);
res.pa = right.pa + left.pa - n;
res.pc = left.pc + right.pc - n;
return res;
}
void buildTree(node *tree,string a,int index,int s,int e)
{
//base case
if(s>e) return;
//reached leaf node
if(s==e)
{
if(a[s]==')') { tree[index].pc=1; tree[index].pa=0;}
else { tree[index].pa=1;tree[index].pc=0; }
return ;
}
//now build the segment tree in bottom up manner
int m = (s+e)/2;
buildTree(tree,a,2*index,s,m);
buildTree(tree,a,2*index+1,m+1,e);
node left = tree[2*index]; node right = tree[2*index+1];
tree[index]=join(left,right);
return;
}

//function to query the segment tree for RSQ
node query(node *tree,int index,int s,int e,int qs,int qe)
{
//base case: if query range is outside the node range
if(qs>e || s>qe) return node{INF,INF};
//complete overlap
if(s>=qs && e<=qe) return tree[index];
//now partial overlap case is executed
int m = (s+e)/2;
node left = query(tree,2*index,s,m,qs,qe);
node right = query(tree,2*index+1,m+1,e,qs,qe);
return join(left,right);
}

void updateNode(node *tree,int index,int s,int e,int pos)
{
if(pos<s || pos>e) return ;
if(s==e)
{
if(tree[index].pc==1) { tree[index].pc=0; tree[index].pa=1; }
else { tree[index].pc=1; tree[index].pa=0; }
return;
}
int m = (s+e)/2;
updateNode(tree,2*index,s,m,pos);
updateNode(tree,2*index+1,m+1,e,pos);
tree[index] = join(tree[2*index],tree[2*index+1]);
return;
}
int main()
{
int n,c,ca=1;
while(scanf("%d",&n)==1)
{
string a;
cin.ignore();
getline(cin,a);
node*tree = new node[4*n+1];                                    //array to store the segment tree
int index = 1;												  //index of 1st node
int s =0,e=n-1;
buildTree(tree,a,index,s,e);								  //now tree has been built
scanf("%d",&c);
printf("Test %d:\n",ca++);
for(int i=0; i<c;i++)
{
int f; scanf("%d",&f);
if(f==0)
{
node aux = query(tree,index,s,e,0,n);
if(aux.pa==0 && aux.pc==0) printf("YES\n");
else printf("NO\n");
}
else updateNode(tree,index,s,e,f-1);
}
}
return 0;
}
``````