57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
#include <cassert>
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#include <functional>
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#include <string>
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#include <vector>
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class Solution {
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static auto get_function(const std::string &op)
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-> std::function<int(int, int)> {
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if (op == "+") {
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return std::plus<int>{};
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} else if (op == "-") {
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return std::minus<int>{};
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} else if (op == "*") {
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return std::multiplies<int>{};
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} else if (op == "/") {
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return std::divides<int>{};
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}
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assert(false);
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}
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public:
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auto evalRPN(const std::vector<std::string> &tokens) -> int {
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std::vector<int> stack;
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for (const auto &token : tokens) {
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if (token == "+" || token == "-" || token == "*" || token == "/") {
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assert(stack.size() >= 2);
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int right = stack.back();
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stack.pop_back();
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int left = stack.back();
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stack.pop_back();
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stack.push_back(get_function(token)(left, right));
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} else {
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stack.push_back(std::stoi(token));
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}
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}
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return stack.back();
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}
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};
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int main() {
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Solution s;
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assert(s.evalRPN(std::vector<std::string>{
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{"2"}, {"1"}, {"+"}, {"3"}, {"*"}}) == 9);
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assert(s.evalRPN(std::vector<std::string>{
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{"4"}, {"13"}, {"5"}, {"/"}, {"+"}}) == 6);
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assert(s.evalRPN(std::vector<std::string>{{"10", "6", "9", "3", "+", "-11",
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"*", "/", "*", "17", "+", "5",
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"+"}}) == 22);
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return 0;
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}
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