SPOJ- Counting Triangles Solution

SPOJ - Counting Triangles Problem Solution

Solution:-

#include<bits/stdc++.h>
using namespace std;
#define MAX 1000010

long long up[MAX],down[MAX];

void init()
{
    up[1]=1;
    up[2]=4;
    down[2]=1;

    for(int i=3;i<=MAX;i++)
    {
        up[i]=2*up[i-1]+i-up[i-2];
        down[i]=up[i-1]-down[i-1];
    }
}

int main()
{
    init();
    int tc,num;;
    cin>>tc;
    while(tc--)
    {
        cin>>num;
        cout<<up[num]+down[num]<<endl;
    }
    return 0;
}