November 2013 Bronze Problem 1: Combination Lock

Result: 4/10 *x*xxxx**x

I optimized it near the end, but then I realized that the overlap() function fails when N < 5.

combo.cpp

#include <iostream>
#include <fstream>

#define loopi(x) loop_start(i,x,0)
#define loopj(x) loop_start(j,x,0)
#define loop_start(i, x,s) for(int i = (s); i < (x); ++i)
#define loop_rev(a,x,stop) for(int a = (x); a >= (stop); --a)

using namespace std;

int N;

int overlap(int a, int b){
 return 5 - abs(a - b) % N;
}

#define NUMCOMBO 3
int main() {
 ofstream fout ("combo.out");
 ifstream fin ("combo.in");
 // get input
 int combo1[NUMCOMBO];
 int combo2[NUMCOMBO];
 fin >> N;
 loopi(NUMCOMBO)
  fin >> combo1[i];
 loopi(NUMCOMBO)
  fin >> combo2[i];
 // calculate:
 int overlap_a = overlap(combo1[0], combo2[0]);
 int overlap_b = overlap_a ? overlap(combo1[1], combo2[1]) : 0;
 int overlap_c = overlap_b ? overlap(combo1[2], combo2[2]) : 0;
 // 2 * min(5, N) ** 3, but subtract the overlap
 // write output
 int abc = min(5, N);
 fout << (2 * abc * abc * abc - overlap_a * overlap_b * overlap_c);
 return 0;
}