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AOC2023: Cleanup day9 code 

Move tree building to its own function. Both parts can use the same
tree. This also decreaseas memory usage by one element by row :D
This commit is contained in:
Bananymous 2023-12-09 19:08:13 +02:00
parent 284a012509
commit 99a5b6e2ef
1 changed files with 44 additions and 68 deletions
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112
userspace/aoc2023/day9/main.cpp
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@ -16,7 +16,7 @@ i64 parse_i64(BAN::StringView sv)
bool negative = (!sv.empty() && sv.front() == '-');
if (negative)
sv = sv.substring(1);
i64 result = 0;
for (char c : sv)
{
@ -27,6 +27,37 @@ i64 parse_i64(BAN::StringView sv)
return negative ? -result : result;
}
BAN::Vector<BAN::Vector<i64>> build_difference_tree(BAN::StringView input)
{
auto value_strs = MUST(input.split(' '));
if (value_strs.empty())
return {};
BAN::Vector<BAN::Vector<i64>> tree;
MUST(tree.emplace_back(value_strs.size(), 0));
for (size_t i = 0; i < value_strs.size(); i++)
tree.back()[i] = parse_i64(value_strs[i]);
bool all_zeroes = false;
while (!all_zeroes)
{
size_t last = tree.size();
MUST(tree.emplace_back(tree.back().size() - 1, 0));
all_zeroes = true;
for (size_t i = 0; i < tree.back().size(); i++)
{
i64 lhs = tree[last - 1][i + 0];
i64 rhs = tree[last - 1][i + 1];
tree[last][i] = rhs - lhs;
if (tree[last][i] != 0)
all_zeroes = false;
}
}
return tree;
}
i64 puzzle1(FILE* fp)
{
i64 result = 0;
@ -34,43 +65,15 @@ i64 puzzle1(FILE* fp)
char buffer[128];
while (fgets(buffer, sizeof(buffer), fp))
{
BAN::StringView line(buffer);
auto value_strs = MUST(line.split(' '));
if (value_strs.empty())
auto tree = build_difference_tree(buffer);
if (tree.empty())
continue;
BAN::Vector<BAN::Vector<i64>> values;
MUST(values.emplace_back(value_strs.size() + 1, 0));
for (size_t i = 0; i < value_strs.size(); i++)
values.back()[i] = parse_i64(value_strs[i]);
i64 current = 0;
for (size_t i = tree.size(); i > 0; i--)
current = tree[i - 1].back() + current;
bool all_zeroes = false;
while (!all_zeroes)
{
size_t last = values.size();
MUST(values.emplace_back(values.back().size() - 1, 0));
all_zeroes = true;
for (size_t i = 0; i < values.back().size() - 1; i++)
{
i64 lhs = values[last - 1][i + 0];
i64 rhs = values[last - 1][i + 1];
values[last][i] = rhs - lhs;
if (values[last][i] != 0)
all_zeroes = false;
}
}
for (size_t i = values.size() - 1; i > 0; i--)
{
const size_t len = values[i].size();
i64 lhs = values[i - 1][len - 1];
i64 res = values[i][len - 1];
values[i - 1][len - 0] = res + lhs;
}
result += values.front().back();
result += current;
}
return result;
@ -83,42 +86,15 @@ i64 puzzle2(FILE* fp)
char buffer[128];
while (fgets(buffer, sizeof(buffer), fp))
{
BAN::StringView line(buffer);
auto value_strs = MUST(line.split(' '));
if (value_strs.empty())
auto tree = build_difference_tree(buffer);
if (tree.empty())
continue;
BAN::Vector<BAN::Vector<i64>> values;
MUST(values.emplace_back(value_strs.size() + 1, 0));
for (size_t i = 0; i < value_strs.size(); i++)
values.back()[i + 1] = parse_i64(value_strs[i]);
i64 current = 0;
for (size_t i = tree.size(); i > 0; i--)
current = tree[i - 1].front() - current;
bool all_zeroes = false;
while (!all_zeroes)
{
size_t last = values.size();
MUST(values.emplace_back(values.back().size() - 1, 0));
all_zeroes = true;
for (size_t i = 1; i < values.back().size(); i++)
{
i64 lhs = values[last - 1][i + 0];
i64 rhs = values[last - 1][i + 1];
values[last][i] = rhs - lhs;
if (values[last][i] != 0)
all_zeroes = false;
}
}
for (size_t i = values.size() - 1; i > 0; i--)
{
i64 rhs = values[i - 1][1];
i64 res = values[i][0];
values[i - 1][0] = rhs - res;
}
result += values.front().front();
result += current;
}
return result;