JAVA实现逆波兰转换

在家翻看信息检索的课本，实在太无聊了，还是写代码比较high。

用java实现逆波兰转换之后，感觉对逆波兰转换的步骤记忆更加深刻了，不错，不错~

下面上代码

 1 package com.hicc.lc;

 2 

 3 import java.util.ArrayList;

 4 import java.util.HashMap;

 5 import java.util.List;

 6 import java.util.Map;

 7 import java.util.Stack;

 8 

 9 import com.hicc.lc.vo.Result;

10 

11 public class Generator {

12     // 获得运算符优先级

13     public static int getPriority(String operator) {

14         final int plusPriority = 2;

15         final int multiplyPriority = 3;

16         final int minusPriority = 4;

17         final int leftBracketPriority = 1;

18         if ("+".equals(operator))

19             return plusPriority;

20         if ("*".equals(operator))

21             return multiplyPriority;

22         if ("-".equals(operator))

23             return minusPriority;

24         if ("(".equals(operator))

25             return leftBracketPriority;

26         return 0;

27     }

28 

29     // 比较两运算符优先级

30     public static boolean priorThan(String operatorA, String operatorB) {

31         return getPriority(operatorA) > getPriority(operatorB);

32     }

33 

34     public static void main(String args[]) {

35         String expression = "(a+b+c)*d*-e+f*g";

36 //        String expression = "(A+B)*(C+D)+E";

37         Map<Integer, String> retrivalWords = new HashMap<Integer, String>();// 检索词表存储区

38         Stack<String> operatorList = new Stack<String>();// 算子保留栈

39         List<Result> result = new ArrayList<Result>();// 结果保留栈

40         expression = expression.concat(".");

41         int letterNum = 0;

42         for (int i = 0; i < expression.length(); i++) {

43             String s = String.valueOf(expression.charAt(i));

44             if (s.matches("[a-zA-Z]")) {

45                 letterNum = letterNum + 1;

46             } else {

47                 if (letterNum > 0) {

48                     String retrivalWord = expression

49                             .substring(i - letterNum, i);

50                     retrivalWords.put(retrivalWords.size() + 1, retrivalWord);

51                     result.add(new Result(0, retrivalWord));

52                     letterNum = 0;

53                 }

54                 if ("(".equals(s)) {

55                     operatorList.push("(");

56                 }

57                 if ("+*-".contains(s)) {

58                     while ((!operatorList.isEmpty())

59                             && (!priorThan(s, operatorList.peek()))) {

60                         result.add(new Result(1, operatorList.pop()));

61                     }

62 //                    if((!operatorList.isEmpty())

63 //                            && !s.equals(operatorList.peek()))

64                         operatorList.push(s);

65                 }

66                 if (")".equals(s)) {

67                     while (!operatorList.peek().equals("(")) {

68                         result.add(new Result(1, operatorList.pop()));

69                     }

70                     operatorList.pop();

71                 }

72                 if (".".equals(s)) {

73                     while (!operatorList.isEmpty()) {

74                         result.add(new Result(1, operatorList.pop()));

75                     }

76                     result.add(new Result(1, "."));

77                 }

78 

79             }

80         }

81         System.out.print("输出逆波兰表达式:");

82         for (int j = 0; j < result.size(); j++) {

83             System.out.print(result.get(j).getContent());

84         }

85         System.out.println();

86     }

87 }

package com.hicc.lc.vo;



public class Result {

    private int charactor;

    private String content;



    public Result(int charactor, String content) {

        this.charactor = charactor;

        this.content = content;

    }



    public int getCharactor() {

        return charactor;

    }



    public String getContent() {

        return content;

    }



    public void setCharactor(int charactor) {

        this.charactor = charactor;

    }



    public void setContent(String content) {

        this.content = content;

    }

}

很久不编程了，各种数据结构都已经记混了，如果有人认为上面的代码有哪里需要改进的欢迎指正.