逆波兰计算器完整版

r囧r小猫 2021-07-24 16:04 387阅读 0赞

# 一 需求 #

完整版的逆波兰计算器，功能包括如下：

1 支持 + - \* / ( )

2 多位数，支持小数

3 兼容处理, 过滤任何空白字符，包括空格、制表符、换页符

# 二 代码 #

import java.util.ArrayList;
    import java.util.Collections;
    import java.util.List;
    import java.util.Stack;
    import java.util.regex.Pattern;
    
    /**
     * @className: ReversePolishMultiCalc
     * @description: 逆波兰计算器完整版
     * @date: 2021/3/6
     * @author: cakin
     */
    public class ReversePolishMultiCalc {
    
        /**
         * 匹配 + - * / ( ) 运算符
         */
        static final String SYMBOL = "\\+|-|\\*|/|\$|\$";
    
        static final String LEFT = "(";
        static final String RIGHT = ")";
        static final String ADD = "+";
        static final String MINUS = "-";
        static final String TIMES = "*";
        static final String DIVISION = "/";
    
        /**
         * 加減 + -
         */
        static final int LEVEL_01 = 1;
        /**
         * 乘除 * /
         */
        static final int LEVEL_02 = 2;
    
        /**
         * 括号
         */
        static final int LEVEL_HIGH = Integer.MAX_VALUE;
    
    
        static Stack<String> stack = new Stack<>();
        static List<String> data = Collections.synchronizedList(new ArrayList<String>());
    
        /**
         * 去除所有空白符
         *
         * @param s
         * @return
         */
        public static String replaceAllBlank(String s) {
            // \\s+ 匹配任何空白字符，包括空格、制表符、换页符等等, 等价于[ \f\n\r\t\v]
            return s.replaceAll("\\s+", "");
        }
    
        /**
         * 判断是不是数字 int double long float
         *
         * @param s
         * @return
         */
        public static boolean isNumber(String s) {
            Pattern pattern = Pattern.compile("^[-\\+]?[.\\d]*$");
            return pattern.matcher(s).matches();
        }
    
        /**
         * 判断是不是运算符
         *
         * @param s
         * @return
         */
        public static boolean isSymbol(String s) {
            return s.matches(SYMBOL);
        }
    
        /**
         * 匹配运算等级
         *
         * @param s
         * @return
         */
        public static int calcLevel(String s) {
            if ("+".equals(s) || "-".equals(s)) {
                return LEVEL_01;
            } else if ("*".equals(s) || "/".equals(s)) {
                return LEVEL_02;
            }
            return LEVEL_HIGH;
        }
    
        /**
         * 匹配
         *
         * @param s
         * @throws Exception
         */
        public static List<String> doMatch(String s) throws Exception {
            if (s == null || "".equals(s.trim())) throw new RuntimeException("data is empty");
            if (!isNumber(s.charAt(0) + "")) throw new RuntimeException("data illeagle,start not with a number");
            s = replaceAllBlank(s);
            String each;
            int start = 0;
            for (int i = 0; i < s.length(); i++) {
                if (isSymbol(s.charAt(i) + "")) {
                    each = s.charAt(i) + "";
                    // 栈为空，(操作符，或者 操作符优先级大于栈顶优先级 && 操作符优先级不是( )的优先级 及是 ) 不能直接入栈
                    if (stack.isEmpty() || LEFT.equals(each)
                            || ((calcLevel(each) > calcLevel(stack.peek())) && calcLevel(each) < LEVEL_HIGH)) {
                        stack.push(each);
                    } else if (!stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek())) {
                        // 栈非空，操作符优先级小于等于栈顶优先级时出栈入列，直到栈为空，或者遇到了(，最后操作符入栈
                        while (!stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek())) {
                            if (calcLevel(stack.peek()) == LEVEL_HIGH) {
                                break;
                            }
                            data.add(stack.pop());
                        }
                        stack.push(each);
                    } else if (RIGHT.equals(each)) {
                        // ) 操作符，依次出栈入列直到空栈或者遇到了第一个)操作符，此时)出栈
                        while (!stack.isEmpty() && LEVEL_HIGH >= calcLevel(stack.peek())) {
                            if (LEVEL_HIGH == calcLevel(stack.peek())) {
                                stack.pop();
                                break;
                            }
                            data.add(stack.pop());
                        }
                    }
                    start = i; // 前一个运算符的位置
                } else if (i == s.length() - 1 || isSymbol(s.charAt(i + 1) + "")) {
                    each = start == 0 ? s.substring(start, i + 1) : s.substring(start + 1, i + 1);
                    if (isNumber(each)) {
                        data.add(each);
                        continue;
                    }
                    throw new RuntimeException("data not match number");
                }
            }
            // 如果栈里还有元素，此时元素需要依次出栈入列，可以想象栈里剩下栈顶为/，栈底为+，应该依次出栈入列，可以直接翻转整个stack 添加到队列
            Collections.reverse(stack);
            data.addAll(new ArrayList<>(stack));
    
            System.out.println(data);
            return data;
        }
    
        /**
         * 算出结果
         *
         * @param list 逆波兰表达是
         * @return Double 计算结果
         */
        public static Double doCalc(List<String> list) {
            Double d = 0d;
            if (list == null || list.isEmpty()) {
                return null;
            }
            if (list.size() == 1) {
                System.out.println(list);
                d = Double.valueOf(list.get(0));
                return d;
            }
            ArrayList<String> list1 = new ArrayList<>();
            for (int i = 0; i < list.size(); i++) {
                list1.add(list.get(i));
                if (isSymbol(list.get(i))) {
                    Double d1 = doTheMath(list.get(i - 2), list.get(i - 1), list.get(i));
                    list1.remove(i);
                    list1.remove(i - 1);
                    list1.set(i - 2, d1 + "");
                    list1.addAll(list.subList(i + 1, list.size()));
                    break;
                }
            }
            doCalc(list1);
            return d;
        }
    
        /**
         * 运算
         *
         * @param s1
         * @param s2
         * @param symbol
         * @return
         */
        public static Double doTheMath(String s1, String s2, String symbol) {
            Double result;
            switch (symbol) {
                case ADD:
                    result = Double.valueOf(s1) + Double.valueOf(s2);
                    break;
                case MINUS:
                    result = Double.valueOf(s1) - Double.valueOf(s2);
                    break;
                case TIMES:
                    result = Double.valueOf(s1) * Double.valueOf(s2);
                    break;
                case DIVISION:
                    result = Double.valueOf(s1) / Double.valueOf(s2);
                    break;
                default:
                    result = null;
            }
            return result;
        }
    
        /**
         * 功能描述：完整版逆波兰计算器测试
         *
         * @param args 命令行
         * @author cakin
         * @date 2021/3/6
         */
        public static void main(String[] args) {
            // String math = "9+(3-1)*3+10/2";
            String math = "12.8 + (2 - 3.55)*4+10/5.0";
            try {
                doCalc(doMatch(math));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

# 三 测试结果 #

[12.8, 2, 3.55, -, 4, *, +, 10, 5.0, /, +]
    [8.600000000000001]