code-advent-1.cpp

#include <cassert>
#include <iostream>
#include <stdio.h>
#include <string>
#include <vector>

std::vector<int> toVector(const std::string& str) {
	std::vector<int> result;
	for (auto c : str) {
		result.push_back(c - '0');
	}
	return result;
}

#if 0
int sumAdjacent(const std::string& str) {
	if (str.size() < 2) return 0;
	auto v = toVector(str);
	int sum = 0;
	int last = v[0];
	int curr = 0;
	int adjCount = 1;
	bool adj = false;

	for (auto it = v.begin() + 1; it != v.end(); ++it) {
		curr = *it;
		adj = curr == last;

		printf("last=%d curr=%d adj=%d adjCount=%d\n", last, curr, (int) adj, adjCount);
		if (!adj && adjCount > 1) {
			printf("changed %d * %d\n", adjCount, curr);
			sum += adjCount * last;
		}

		adjCount = adj ? adjCount + 1 : 1;
		last = curr;
	}

	if (adjCount > 1) {
		printf("finish %d * %d\n", adjCount, curr);
		sum += adjCount * last;
	}

	printf("sum of %s = %d\n", str.c_str(), sum);
	return sum;
}
#endif

std::vector<std::vector<int>> group(const std::vector<int>& v) {
	std::vector<std::vector<int>> result;
	std::vector<int> currGroup;
	int last = 0;
	for (auto n : v) {
		if (last == n) {
			currGroup.push_back(n);
		} else {
			if (!currGroup.empty()) {
				result.push_back(std::move(currGroup));
			}
			currGroup.clear();
			currGroup.push_back(n);
		}
		last = n;
	}
	result.push_back(std::move(currGroup));

  if (result.size() > 2) {
    auto& f = result.front();
    auto& b = result.back();
    if (f.front() == b.back()) {
      f.insert(f.end(), b.begin(), b.end());
    }
    result.resize(result.size() - 1);
  }

	for (auto g : result) {
		printf("[");
		for (auto n : g) {
			printf("%d,", n);
		}
		printf("] ");
	}
	return result;
}

int sumAdjacent(const std::string& str) {
	if (str.size() < 2) return 0;
	auto v = toVector(str);
	auto groups = group(v);
  int sum = 0;
  for (auto& g: groups) {
    if (g.size() > 2) {
      sum += g.front() * g.size();
    } else if (g.size() > 1) {
      sum += g.front();
    }
  }
  printf("sum of %s is %d\n", str.c_str(), sum);
	return sum;
}

int main() {
	assert(sumAdjacent("") == 0);
	assert(sumAdjacent("1") == 0);
	assert(sumAdjacent("1122") == 3);
	assert(sumAdjacent("1111") == 4);
	assert(sumAdjacent("1234") == 0);
	assert(sumAdjacent("91212129") == 9);
	assert(sumAdjacent("991212129") == 27);
}