Parsing/Shunting-yard algorithm: Difference between revisions
→{{header|C sharp}}
Line 760:
Testing string `123' <enter>
^C</pre>
=={{header|C++}}==
{{trans|Java}}
<lang cpp>#include <iostream>
#include <sstream>
#include <stack>
std::string infixToPostfix(const std::string& infix) {
const std::string ops = "-+/*^";
std::stringstream ss;
std::stack<int> s;
std::stringstream input(infix);
std::string token;
while (std::getline(input, token, ' ')) {
if (token.empty()) {
continue;
}
char c = token[0];
size_t idx = ops.find(c);
// check for operator
if (idx != std::string::npos) {
while (!s.empty()) {
int prec2 = s.top() / 2;
int prec1 = idx / 2;
if (prec2 > prec1 || (prec2 == prec1 && c != '^')) {
ss << ops[s.top()] << ' ';
s.pop();
} else break;
}
s.push(idx);
} else if (c == '(') {
s.push(-2); // -2 stands for '('
} else if (c == ')') {
// until '(' on stack, pop operators.
while (s.top() != -2) {
ss << ops[s.top()] << ' ';
s.pop();
}
s.pop();
} else {
ss << token << ' ';
}
}
while (!s.empty()) {
ss << ops[s.top()] << ' ';
s.pop();
}
return ss.str();
}
int main() {
std::string infix = "3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3";
std::cout << "infix: " << infix << '\n';
std::cout << "postfix: " << infixToPostfix(infix) << '\n';
return 0;
}</lang>
{{out}}
<pre>infix: 3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3
postfix: 3 4 2 * 1 5 - 2 3 ^ ^ / +</pre>
=={{header|C sharp}}==
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