标签:reverse notation int evaluate private Stack static final String
题目:
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
解一:
import java.util.Stack; public class Solution { private final static String ADD = "+"; private final static String SUBTRACT = "-"; private final static String MULTIPLY = "*"; private final static String DIVIDE = "/"; public int evalRPN(String[] tokens) { Stack<Integer> stack = new Stack<Integer>(); int op1,op2, result=0; if(tokens.length<3){ return Integer.parseInt(tokens[0]); } for(int i = 0; i<tokens.length; i++){ if (isOperator(tokens[i])){ op2 = (stack.pop()).intValue(); op1 = (stack.pop()).intValue(); result = evaluateSingleOperator(tokens[i],op1,op2); stack.push(new Integer(result)); }else { stack.push(new Integer(Integer.parseInt(tokens[i]))); } } return result; } private boolean isOperator(String token){ return (token.equals("+") || token.equals("-") || token.equals("*") || token.equals("/")); } private int evaluateSingleOperator(String operator, int op1 , int op2){ int result = 0; switch (operator){ case ADD: result = op1 + op2; break; case SUBTRACT: result = op1- op2; break; case MULTIPLY: result = op1 * op2; break; case DIVIDE: result = op1 / op2; break; } return result; } }
标签:reverse,notation,int,evaluate,private,Stack,static,final,String 来源: https://www.cnblogs.com/xww115/p/11195387.html
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