Day15 栈的应用（括号匹配）

1、 charAt() 就是返回指定索引位置的char值；

1     public char charAt(int index) {
2         if ((index < 0) || (index >= value.length)) {
3             throw new StringIndexOutOfBoundsException(index);
4         }
5         return value[index];
6     }

2、在 bracketMatching(String paraString) 里，首先放一个 '#' 进去，之后 '#' 就会一直在栈底，for循环结束之后再取出一个字符，如果这个字符不是 '#' ，就说明匹配失败；

  1 public class CharStack {
  2     /**
  3      * The depth.
  4      */
  5     public static final int MAX_DEPTH = 10;
  6 
  7     /**
  8      * The actual depth.
  9      */
 10     int depth;
 11 
 12     /**
 13      * The data
 14      */
 15     char[] data;
 16 
 17     public CharStack() {
 18         depth = 0;
 19         data = new char[MAX_DEPTH];
 20     }// Of the first constructor
 21 
 22     /**
 23      * Overrides the method claimed in Object, the superclass of any class.
 24      */
 25     public String toString() {
 26         String resultString = "";
 27         for (int i = 0; i < depth; i++) {
 28             resultString += data[i];
 29         } // Of for i
 30 
 31         return resultString;
 32     }// Of toString
 33 
 34     /**
 35      * Push an element.
 36      * 
 37      * @param paraChar The given char.
 38      * @return Success or not.
 39      */
 40     public boolean push(char paraChar) {
 41         if (depth == MAX_DEPTH) {
 42             System.out.println("Stack full.");
 43             return false;
 44         } // Of if
 45 
 46         data[depth] = paraChar;
 47         depth++;
 48 
 49         return true;
 50     }// Of push
 51 
 52     /**
 53      * Pop an element.
 54      * 
 55      * @return The popped char.
 56      */
 57     public char pop() {
 58         if (depth == 0) {
 59             System.out.println("Nothing to pop.");
 60             return '\0';
 61         } // Of if
 62 
 63         char resultChar = data[depth - 1];
 64         depth--;
 65 
 66         return resultChar;
 67     }// Of pop
 68 
 69     public static boolean bracketMatching(String paraString) {
 70         // Step 1. Initialize the stack through pushing a '#' at the bottom.
 71         CharStack tempStack = new CharStack();
 72         tempStack.push('#');
 73         char tempChar, tempPoppedChar;
 74 
 75         // Step 2. Process the string. For a string, length() is a method
 76         // instead of a member variable
 77         for (int i = 0; i < paraString.length(); i++) {
 78             tempChar = paraString.charAt(i);
 79 
 80             switch (tempChar) {
 81                 case '(':
 82                 case '[':
 83                 case '{':
 84                     tempStack.push(tempChar);
 85                     break;
 86                 case ')':
 87                     tempPoppedChar = tempStack.pop();
 88                     if (tempPoppedChar != '(') {
 89                         return false;
 90                     }// Of if
 91                     break;
 92                 case ']':
 93                     tempPoppedChar = tempStack.pop();
 94                     if (tempPoppedChar != '[') {
 95                         return false;
 96                     }// Of if
 97                     break;
 98                 case '}':
 99                     tempPoppedChar = tempStack.pop();
100                     if (tempPoppedChar != '{') {
101                         return false;
102                     }// Of if
103                     break;
104                 default:
105                     // Do nothing.
106             }// Of Switch
107         }// Of for i
108 
109         tempPoppedChar = tempStack.pop();
110         if (tempPoppedChar != '#') {
111             return false;
112         }// Of if
113         
114         return true;
115     }// Of bracketMatching
116 
117     /**
118      * The entrance of the program.
119      * 
120      * @param args
121      */
122     public static void main(String args[]) {
123         CharStack tempStack = new CharStack();
124 
125         for (char ch = 'a'; ch < 'm'; ch++) {
126             tempStack.push(ch);
127             System.out.println("The current stack is: " + tempStack);
128         } // Of for ch
129 
130         char tempChar;
131         for (int i = 0; i < 12; i++) {
132             tempChar = tempStack.pop();
133             System.out.println("Popped: " + tempChar);
134             System.out.println("The current stack is: " + tempStack);
135         } // Of for i
136 
137         boolean tempMatch;
138         String tempExpression = "[2 + (1 - 3)] * 4";
139         tempMatch = bracketMatching(tempExpression);
140         System.out.println("Is the expression " + tempExpression + "bracket matching? " + tempMatch);
141 
142         tempExpression = "( ))";
143         tempMatch = bracketMatching(tempExpression);
144         System.out.println("Is the expression " + tempExpression + "bracket matching? " + tempMatch);
145 
146         tempExpression = "()()(())";
147         tempMatch = bracketMatching(tempExpression);
148         System.out.println("Is the expression " + tempExpression + "bracket matching? " + tempMatch);
149         
150         tempExpression = "({}[])";
151         tempMatch = bracketMatching(tempExpression);
152         System.out.println("Is the expression " + tempExpression + "bracket matching? " + tempMatch);
153         
154         tempExpression = ")(";
155         tempMatch = bracketMatching(tempExpression);
156         System.out.println("Is the expression " + tempExpression + "bracket matching? " + tempMatch);
157         
158     }// Of main
159 
160 }// Of CharStack

 

posted @ 2022-05-03 00:04  滑稽的炒饭  阅读(27)  评论(0)    收藏  举报