# UVa : 12238 – Ants Colony

Problem Link : http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=3390

```
#include &lt;bits/stdc++.h&gt;

#define pii              pair &lt;int,int&gt;
#define pll              pair &lt;long long,long long&gt;
#define sc               scanf
#define pf               printf
#define Pi               2*acos(0.0)
#define ms(a,b)          memset(a, b, sizeof(a))
#define pb(a)            push_back(a)
#define MP               make_pair
#define db               double
#define ll               long long
#define EPS              10E-10
#define ff               first
#define ss               second
#define sqr(x)           (x)*(x)
#define D(x)             cout&lt;&lt;#x &quot; = &quot;&lt;&lt;(x)&lt;&lt;endl
#define VI               vector &lt;int&gt;
#define DBG              pf(&quot;Hi\n&quot;)
#define MOD              1000000007
#define CIN              ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define SZ(a)            (int)a.size()
#define sf(a)            scanf(&quot;%d&quot;,&amp;a)
#define sfl(a)           scanf(&quot;%lld&quot;,&amp;a)
#define sff(a,b)         scanf(&quot;%d %d&quot;,&amp;a,&amp;b)
#define sffl(a,b)        scanf(&quot;%lld %lld&quot;,&amp;a,&amp;b)
#define sfff(a,b,c)      scanf(&quot;%d %d %d&quot;,&amp;a,&amp;b,&amp;c)
#define sfffl(a,b,c)     scanf(&quot;%lld %lld %lld&quot;,&amp;a,&amp;b,&amp;c)
#define stlloop(v)       for(__typeof(v.begin()) it=v.begin();it!=v.end();it++)
#define loop(i,n)        for(int i=0;i&lt;n;i++)
#define loop1(i,n)       for(int i=1;i&lt;=n;i++)
#define REP(i,a,b)       for(int i=a;i&lt;b;i++)
#define RREP(i,a,b)      for(int i=a;i&gt;=b;i--)
#define TEST_CASE(t)     for(int z=1;z&lt;=t;z++)
#define PRINT_CASE       printf(&quot;Case %d: &quot;,z)
#define LINE_PRINT_CASE  printf(&quot;Case %d:\n&quot;,z)
#define CASE_PRINT       cout&lt;&lt;&quot;Case &quot;&lt;&lt;z&lt;&lt;&quot;: &quot;
#define all(a)           a.begin(),a.end()
#define intlim           2147483648
#define infinity         (1&lt;&lt;28)
#define ull              unsigned long long
#define gcd(a, b)        __gcd(a, b)
#define lcm(a, b)        ((a)*((b)/gcd(a,b)))

using namespace std;

/*----------------------Graph Moves----------------*/
//const int fx[]={+1,-1,+0,+0};
//const int fy[]={+0,+0,+1,-1};
//const int fx[]={+0,+0,+1,-1,-1,+1,-1,+1};   // Kings Move
//const int fy[]={-1,+1,+0,+0,+1,+1,-1,-1};  // Kings Move
//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move
//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move
/*------------------------------------------------*/

/*-----------------------Bitmask------------------*/
//int Set(int N,int pos){return N=N | (1&lt;&lt;pos);}
//int reset(int N,int pos){return N= N &amp; ~(1&lt;&lt;pos);}
//bool check(int N,int pos){return (bool)(N &amp; (1&lt;&lt;pos));}
/*------------------------------------------------*/

#define mx 100005

int n;
int level[mx],par[mx],dis[mx];

vector&lt;int&gt;g[mx],cost[mx];

ll sparse_par[mx][20],sparse_sum[mx][20];

void dfs(int u, int cnt, int from)
{
par[u]=from;
level[u]=cnt;

for(int i=0;i&lt;SZ(g[u]);i++)
{
int v=g[u][i];

if(v!=from)
{
dis[v]=cost[u][i];
dfs(v,cnt+1,u);
}

}

}

void build_table()
{
for(int i=0;i&lt;n;i++)
{
sparse_par[i][0]=par[i];
sparse_sum[i][0]=dis[i];
}

for(int j=1;1&lt;&lt;j&lt;n;j++)
{
for(int i=0;i&lt;n;i++)
{
sparse_par[i][j]=sparse_par[sparse_par[i][j-1]][j-1];
sparse_sum[i][j]=sparse_sum[i][j-1]+sparse_sum[sparse_par[i][j-1]][j-1];
//            D(i);
//            D(j);
//            D(sparse_par[i][j]);
//            D(sparse_sum[i][j]);
}
}

}

ll query(int p, int q)
{
ll ret=0;
if(level[p]&lt;=level[q]) swap(p,q);

int log=log2(level[p]);

for(int i=log;i&gt;=0;i--)
{
if(level[p]-(1&lt;&lt;i)&gt;=level[q])
{
ret+=sparse_sum[p][i];
p=sparse_par[p][i];
}
}

if(p==q) return ret;

for(int i=log;i&gt;=0;i--)
{
if(sparse_par[p][i]!=sparse_par[q][i])
{
ret+=sparse_sum[p][i];
ret+=sparse_sum[q][i];
p=sparse_par[p][i];
q=sparse_par[q][i];
}
}

ret+=dis[p];
ret+=dis[q];
return ret;

}

int main()
{

//    freopen(&quot;in.txt&quot;,&quot;r&quot;,stdin);
///freopen(&quot;out.txt&quot;,&quot;w&quot;,stdout);

while(sf(n) &amp;&amp; n)
{
for(int i=1;i&lt;n;i++)
{
int a,b;
sff(a,b);
g[i].pb(a);
g[a].pb(i);
cost[a].pb(b);
cost[i].pb(b);
}

dis[0]=0;

dfs(0,0,0);

build_table();

int q;
sf(q);

bool test=1;

while(q--)
{
int a,b;
sff(a,b);

ll ans=query(a,b);

if(test)
{
printf(&quot;%lld&quot;,ans);
test=0;
}
else
{
printf(&quot; %lld&quot;,ans);
}

}

printf(&quot;\n&quot;);

for(int i=0;i&lt;=n;i++)
{
g[i].clear();
cost[i].clear();
}

}

return 0;
}

```
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