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advent-of-code-2020
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Add day 18 part 2

master
Nick Krichevsky 2020-12-18 21:06:47 -05:00
parent 635cd054b9
commit 3d9a06db27
1 changed files with 110 additions and 26 deletions
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136
day18/day18.cpp
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@ -12,11 +12,10 @@
#include <string>
#include <vector>
enum Operation { ADDITION = '+', MULTIPLICATION = '*' };
enum Operation { ADDITION = '+', MULTIPLICATION = '*', IDENTITY = 'i' };
class ExpressionNode;
using EvaluationStrategy = std::function<double(
const ExpressionNode &, const std::unique_ptr<ExpressionNode> &, const std::unique_ptr<ExpressionNode> &,
Operation)>;
using EvaluationStrategy =
std::function<double(const std::unique_ptr<ExpressionNode> &, const std::unique_ptr<ExpressionNode> &, Operation)>;
class ExpressionNode {
public:
@ -24,7 +23,8 @@ class ExpressionNode {
}
virtual long evaluate() const = 0;
virtual int numChildren() const = 0;
virtual std::vector<std::reference_wrapper<const ExpressionNode>> getChildren() const = 0;
virtual Operation getOperation() const = 0;
virtual ~ExpressionNode() {
}
@ -35,12 +35,16 @@ class ValueNode : public ExpressionNode {
ValueNode(long n) : n(n) {
}
long evaluate() const {
long evaluate() const override {
return n;
}
int numChildren() const {
return 1;
std::vector<std::reference_wrapper<const ExpressionNode>> getChildren() const override {
return std::vector<std::reference_wrapper<const ExpressionNode>>{*this};
}
Operation getOperation() const {
return IDENTITY;
}
private:
@ -49,7 +53,7 @@ class ValueNode : public ExpressionNode {
class ExpressionTree : public ExpressionNode {
public:
ExpressionTree(EvaluationStrategy strategy) : strategy(strategy) {
ExpressionTree(EvaluationStrategy strategy) : strategy(strategy), isParenthesized(false) {
}
void setLeft(std::unique_ptr<ExpressionNode> &&left) {
@ -60,8 +64,8 @@ class ExpressionTree : public ExpressionNode {
this->right = std::move(left);
}
int numChildren() const {
return 2;
void setIsParenthesized(bool isParenthesized) {
this->isParenthesized = isParenthesized;
}
void putNextNode(std::unique_ptr<ExpressionNode> &&node) {
@ -78,7 +82,7 @@ class ExpressionTree : public ExpressionNode {
this->op = op;
}
long evaluate() const {
long evaluate() const override {
if (!this->canFullyEvaluate()) {
if (this->left) {
return this->left->evaluate();
@ -89,16 +93,43 @@ class ExpressionTree : public ExpressionNode {
}
}
if (!this->strategy) {
throw "AAA";
return this->strategy(this->left, this->right, *(this->op));
}
std::vector<std::reference_wrapper<const ExpressionNode>> getChildren() const override {
if (!this->left && !this->right) {
throw "Cannot evaluate empty tree's children";
} else if (this->left && this->right) {
return std::vector<std::reference_wrapper<const ExpressionNode>>{
*this->left,
*this->right,
};
} else if (this->left) {
return std::vector<std::reference_wrapper<const ExpressionNode>>{
*this->left,
};
} else if (this->right) {
return std::vector<std::reference_wrapper<const ExpressionNode>>{
*this->right,
};
} else {
throw "Invalid state";
}
return this->strategy(*this, this->left, this->right, *(this->op));
}
Operation getOperation() const {
if (!this->op) {
throw "Cannot get an unset operator";
}
return *this->op;
}
private:
std::unique_ptr<ExpressionNode> left;
std::unique_ptr<ExpressionNode> right;
std::optional<Operation> op;
bool isParenthesized;
EvaluationStrategy strategy;
bool canFullyEvaluate() const {
@ -134,8 +165,8 @@ std::optional<Operation> parseOperator(const std::string_view component) {
std::optional<long> parseNumber(const std::string_view component) {
try {
// This will only really ever copy some (usually small) number of digits... I don't consider it a very expensive
// copy
// This will only really ever copy some (usually small) number of digits... I don't consider it a very
// expensive copy
return std::stol(std::string(component));
} catch (std::invalid_argument) {
return std::nullopt;
@ -167,7 +198,7 @@ std::optional<std::pair<std::string_view, int>> parseParenthetical(int cursor, c
}
std::unique_ptr<ExpressionNode> buildTree(
const std::string_view input, const EvaluationStrategy &strategy, int depth = 0) {
const std::string_view input, const EvaluationStrategy &strategy, bool inParenthetical = false, int depth = 0) {
if (std::count_if(input.cbegin(), input.cend(), [](char c) { return c == ' '; }) == 0) {
std::cout << std::string(depth, ' ') << "RIGHT: " << input << std::endl;
std::optional<long> value = parseNumber(input);
@ -178,10 +209,8 @@ std::unique_ptr<ExpressionNode> buildTree(
return std::make_unique<ValueNode>(*value);
}
if (!strategy) {
throw "AAAA";
}
ExpressionTree tree(strategy);
tree.setIsParenthesized(inParenthetical);
// This should technically be size_type but I need to be able to go before zero
int cursor = input.size() - 1;
while (cursor > 0) {
@ -196,7 +225,7 @@ std::unique_ptr<ExpressionNode> buildTree(
parseParenthetical(previousSpace - 1, input);
if (parentheticalPart) {
std::cout << std::string(depth, ' ') << "RIGHT (paren): " << parentheticalPart->first << std::endl;
auto parentheticalTree = buildTree(parentheticalPart->first, strategy, depth + 1);
auto parentheticalTree = buildTree(parentheticalPart->first, strategy, true, depth + 1);
tree.setRight(std::move(parentheticalTree));
cursor = parentheticalPart->second - 2;
continue;
@ -208,7 +237,7 @@ std::unique_ptr<ExpressionNode> buildTree(
tree.setOp(*componentOperation);
auto rest = input.substr(0, cursor + 1);
std::cout << std::string(depth, ' ') << "LEFT: " << component << std::endl;
auto rightTree = buildTree(rest, strategy, depth + 1);
auto rightTree = buildTree(rest, strategy, false, depth + 1);
tree.setLeft(std::move(rightTree));
// Once we have found an operator and the operand to the left of it, we're done
break;
@ -234,8 +263,7 @@ long run(const std::vector<std::string> &input, const EvaluationStrategy &strate
}
long part1(const std::vector<std::string> &input) {
EvaluationStrategy strategy = [](const ExpressionNode &self,
const std::unique_ptr<ExpressionNode> &left,
EvaluationStrategy strategy = [](const std::unique_ptr<ExpressionNode> &left,
const std::unique_ptr<ExpressionNode> &right,
Operation op) -> long {
long leftValue = left->evaluate();
@ -253,6 +281,61 @@ long part1(const std::vector<std::string> &input) {
return run(input, strategy);
}
long part2(const std::vector<std::string> &input) {
EvaluationStrategy strategy = [](const std::unique_ptr<ExpressionNode> &left,
const std::unique_ptr<ExpressionNode> &right,
Operation op) -> long {
auto leftChildren = left->getChildren();
if (leftChildren.size() == 1 && op == ADDITION) {
return leftChildren.at(0).get().evaluate() + right->evaluate();
} else if (leftChildren.size() == 1 && op == MULTIPLICATION) {
return leftChildren.at(0).get().evaluate() * right->evaluate();
} else if (leftChildren.size() != 2) {
throw std::invalid_argument("Cannot perform unknown binary operation on children");
}
if (op == MULTIPLICATION) {
return right->evaluate() * left->evaluate();
} else if (op != ADDITION && left->getOperation() != MULTIPLICATION) {
throw std::invalid_argument("Cannot perform an unknown binary operation on children");
}
ExpressionNode const *prevCursor = nullptr;
ExpressionNode const *cursor = left.get();
long total = right->evaluate();
while (cursor->getChildren().size() == 2 && cursor->getOperation() == ADDITION) {
auto cursorChildren = cursor->getChildren();
const ExpressionNode &leftCursorChild = cursorChildren.at(0);
const ExpressionNode &rightCursorChild = cursorChildren.at(1);
total += rightCursorChild.evaluate();
prevCursor = cursor;
cursor = &leftCursorChild;
}
if (cursor->getChildren().size() == 1) {
const ExpressionNode &cursorChild = cursor->getChildren().at(0);
Operation finalOperation = op;
if (prevCursor) {
finalOperation = prevCursor->getOperation();
}
if (finalOperation == ADDITION) {
return total + cursorChild.evaluate();
} else if (finalOperation == MULTIPLICATION) {
return total * cursorChild.evaluate();
} else {
throw std::invalid_argument("Cannot perform an unknown binary operation on total");
}
}
auto cursorChildren = cursor->getChildren();
const ExpressionNode &leftCursorChild = cursorChildren.at(0);
const ExpressionNode &rightCursorChild = cursorChildren.at(1);
return (total + rightCursorChild.evaluate()) * leftCursorChild.evaluate();
};
return run(input, strategy);
}
int main(int argc, char *argv[]) {
if (argc != 2) {
@ -262,5 +345,6 @@ int main(int argc, char *argv[]) {
auto input = readInput(argv[1]);
std::cout << part1(input) << std::endl;
// std::cout << part1(input) << std::endl;
std::cout << part2(input) << std::endl;
}