day 03 redo.cpp

// day3_redo.cpp : Defines the entry point for the console application.
// Advent of Code 2017
// http://adventofcode.com/

#include <iostream>
#include <string>
#include <limits>
#include <vector>
#include <map>

typedef enum dir {e=0,n,w,s} direction;
direction next_dir[] = {n,w,s,e};
direction d=e;
int x=0, y=0, count=1, done=0;

// kinda ugly generator of spiral coords
void next_coord(int& x, int&y)
{
	x += d==e ? 1 : (d==w) ? -1 : 0;		// east or west
	y += d==n ? 1 : (d==s) ? -1 : 0;		// north or south
	if (++done==count) done=0;				// moved required number of spots
	if (!done && (d==n || d==s)) count++;	// bump count on n or s
	if (!done) d = next_dir[d];				// switch direction
}

// get a value and iterate through the spiral, counting the x,y
// distance is then just abs(x)+abs(y)
int main1(int argc, char* argv[])
{
	std::cout << "Enter value (-1 to quit part 1)" << std::endl;
	int val;
	while (1) {
		std::cin >> val;
		if (val==-1) break;
		for (int i=1; i<val; ++i) {
			next_coord(x,y);
		}
		std::cout << "Distance is " << abs(x)+abs(y) << std::endl;
	}
	return 0;
}

// track spiral totals in part 2
std::map<std::string,int> sum;

// x,y -> "x,y" 
std::string idx(int x,int y)
{
	std::string idx = std::to_string((long long)x);
	idx.push_back(',');
	idx.append(std::to_string((long long)y));
	return idx;
}

// lookup a sum at cell x,y
int lookup(int x, int y)
{
	std::string id = idx(x,y);
	if (sum.find(id)!=sum.end())
		return sum[id];
	return 0;
}

// sum the 8 neighbors of x,y and save it
int save_sum(int x,int y)
{
	int tot=lookup(x-1,y-1)+lookup(x,y-1)+lookup(x+1,y-1)+lookup(x-1,y+1)+lookup(x,y+1)+lookup(x+1,y+1)+lookup(x-1,y)+lookup(x+1,y);
	return (sum[idx(x,y)]=tot);
}

int main2(int argc, char* argv[])
{
	sum[idx(0,0)] = 1;

	std::cout << "Enter value (-1 to quit part 2)" << std::endl;
	int val,sum;
	while (1) {
		std::cin >> val;
		if (val==-1) break;

		d=e, x=0, y=0, count=1, done=0;
		do {
			next_coord(x,y);
			sum = save_sum(x,y);
		} while (sum<=val);

		std::cout << "Value is " << sum << std::endl;
	}
	return 0;
}

int main(int argc, char* argv[])
{
	main1(argc,argv);
	main2(argc,argv);
}