Data-Structures/Stack/evaluation_prefix.cpp at master · coderhersh/Data-Structures · GitHub

43 lines (35 loc) · 973 Bytes

#include <bits/stdc++.h>

using namespace std;

bool isOperator(char c) {

if (c == '*' || c == '/' || c == '+' || c == '-' || c == '^') {

return true;

}

return false;

}

int evaluate(int second, char o, int first) {

switch (o) {

case '+': return second + first;

case '-': return second - first;

case '*': return second * first;

case '/': return second / first;

case '^': return pow(second, first);

}

int prefixEvaluation(string &String) {

stack<int> Stack;

for (int i = String.size() - 1; i >= 0; --i) {

if (!isOperator(String[i])) {

Stack.push(int(String[i] - '0'));

} else {

int first = Stack.top();

Stack.pop();

int second = Stack.top();

Stack.pop();

Stack.push(evaluate(second, String[i], first));

}

return Stack.top();

}

int main(void) {

return 0;

}

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