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[LeetCode]Evaluate Reverse Polish Notation
Evaluate the value of an arithmetic expression in Reverse Polish Notation.
Valid operators are +
, -
, *
, /
. Each operand may be an integer or another expression.
Some examples:
["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9 ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6
public class Solution { public int evalRPN(String[] tokens) { Stack<Integer> stack = new Stack<Integer>(); for (int i = 0; i < tokens.length; i++) { if (tokens[i].equals("+")) { int a = stack.pop(); int b = stack.pop(); int res = b + a; stack.push(res); } else if (tokens[i].equals("-")) { int a = stack.pop(); int b = stack.pop(); int res = b - a; stack.push(res); } else if (tokens[i].equals("*")) { int a = stack.pop(); int b = stack.pop(); int res = b * a; stack.push(res); } else if (tokens[i].equals("/")) { int a = stack.pop(); int b = stack.pop(); int res = b / a; stack.push(res); } else { stack.push(Integer.parseInt(tokens[i])); } } return stack.peek(); } }
[LeetCode]Evaluate Reverse Polish Notation
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