Evaluate reverse polish notation gfg

This article is tagged with: Evaluate reverse polish notation gfg and lua

evaluate reverse polish notation gfg

["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6

evaluate reverse polish notation gfg

public class Test {
 
public static void main(String[] args) throws IOException {
String[] tokens = new String[] { "2", "1", "+", "3", "*" };
System.out.println(evalRPN(tokens));
}
 
public static int evalRPN(String[] tokens) {
int returnValue = 0;
String operators = "+-*/";
 
Stack<string> stack = new Stack<string>();
 
for (String t : tokens) {
if (!operators.contains(t)) { //push to stack if it is a number
stack.push(t);
} else {//pop numbers from stack if it is an operator
int a = Integer.valueOf(stack.pop());
int b = Integer.valueOf(stack.pop());
switch (t) {
case "+":
stack.push(String.valueOf(a + b));
break;
case "-":
stack.push(String.valueOf(b - a));
break;
case "*":
stack.push(String.valueOf(a * b));
break;
case "/":
stack.push(String.valueOf(b / a));
break;
}
}
}
 
returnValue = Integer.valueOf(stack.pop());
 
return returnValue;
}
}</string></string>

This article is tagged with: Evaluate reverse polish notation gfg and lua