Day19 字符串匹配

1.这个是朴素模式匹配算法，从主串头开始，依次选取和模式串等长的子串，挨个字符匹配，如果匹配失败就检索下一个子串。 2.匹配第一个字符的长度是 length - paraMyString.length + 1。比如主串是ABCDE，模式串是ACB，这里的第一个循环就应该比对 5 - 3 + 1 = 3次。如果第一个字符匹配就依次往后比对，所以第二个循环的比对次数就是模式串的长度 paraMyString.length 次。比如主串是ABCDCDE，模式串是CDE，这里第一个循环比对5次，第二个循环比对3次。 3.这里判断两字符相同 data[i + j] != paraMyString.data[j]，这里在③就执行 tempMatch = false。如果没有匹配失败的就返回位置i了。

 

4.这里求子串for循环里的赋值用的是 resultMyString.data[i] = data[paraStartPosition + i]，注意这里的下标; 5.转义符可以打印引号，还可以用转义符加数字打印ASCII码。

  1 public class MyString {
  2     /**
  3      * The maximal length.
  4      */
  5     public static final int MAX_LENGTH = 10;
  6 
  7     /**
  8      * The actual length.
  9      */
 10     int length;
 11 
 12     /**
 13      * The data.
 14      */
 15     char[] data;
 16 
 17     /**
 18      * Construct an empty char array.
 19      */
 20     public MyString() {
 21         length = 0;
 22         data = new char[MAX_LENGTH];
 23     }// Of the first constructor
 24 
 25     /**
 26      * Construct using a system defined string.
 27      * 
 28      * @param paraString The given sting.
 29      *                   Its length should not exceed MAX_LENGtH - 1.
 30      * 
 31      */
 32     public MyString(String paraString) {
 33         data = new char[MAX_LENGTH];
 34         length = paraString.length();
 35 
 36         for (int i = 0; i < length; i++) {
 37             data[i] = paraString.charAt(i);
 38         } // Of for i
 39     }// Of the second constructor
 40 
 41     public String toString() {
 42         String resultString = "";
 43 
 44         for (int i = 0; i < length; i++) {
 45             resultString += data[i];
 46         } // Of for i
 47 
 48         return resultString;
 49     }// Of toSting
 50 
 51     /**
 52      * Locate the position of a substring.
 53      * 
 54      * @param paraMyString The given substring.
 55      * @return The first position.-1 for no matching.
 56      */
 57     public int locate(MyString paraMyString) {
 58         boolean tempMatch = false;
 59         for (int i = 0; i < length - paraMyString.length + 1; i++) {
 60             //Initialize.
 61             tempMatch = true;
 62             for (int j = 0; j < paraMyString.length; j++) {
 63                 if (data[i + j] != paraMyString.data[j]) {
 64                     tempMatch = false;
 65                     break;
 66                 } // Of if
 67             } // Of for j
 68 
 69             if (tempMatch) {
 70                 return i;
 71             } // Of if
 72         } // Of for i
 73         return -1;
 74     }// Of locate
 75 
 76 
 77     /**
 78      * Get a substring.
 79      * @param paraString The given substring.
 80      * @param paraStartPosition  The start position in the original string.
 81      * @param paraLength The length of the new sting.
 82      * @return The first position.-1 for no matching.
 83      */
 84     public MyString substring(int paraStartPosition, int paraLength) {
 85         if (paraStartPosition + paraLength > length) {
 86             System.out.println("The bound is exceeded");
 87             return null;
 88         } // Of if
 89         
 90         MyString resultMyString = new MyString();
 91         resultMyString.length = paraLength;
 92 
 93         for (int i = 0; i < paraLength; i++) {
 94             resultMyString.data[i] = data[paraStartPosition + i];
 95         } // Of for i
 96 
 97         return resultMyString;
 98     }// Of substring
 99 
100     /**
101      * The entrance of the program
102      * @param args Not used now.
103      */
104     public static void main(String []args) {
105         MyString tempFirstString = new MyString("I like ik.");
106         MyString tempSecondString = new MyString("ik");
107         int tempPosition = tempFirstString.locate(tempSecondString);
108         System.out.println("The position of \"" + tempSecondString + "\" in \"" + tempFirstString + "\" is: " + tempPosition);
109         
110         MyString tempThirdString = new MyString("ki");
111         tempPosition = tempFirstString.locate(tempThirdString);
112         System.out.println("The position of \"" + tempThirdString + "\" in \"" + tempFirstString + "\" is: " + tempPosition);
113 
114         tempThirdString = tempFirstString.substring(1, 2);
115         System.out.println("The substring is: \"" + tempThirdString + "\"");
116         tempThirdString = tempFirstString.substring(5, 5);
117         System.out.println("The substring is: \"" + tempThirdString + "\"");
118         tempThirdString = tempFirstString.substring(5, 6);
119         System.out.println("The substring is: \"" + tempThirdString+ "\"");
120 
121     }// Of main
122 
123 }// Of MySting

 

标签：匹配,int,substring,tempThirdString,length,字符串,MyString,data,Day19
来源： https://www.cnblogs.com/f1uency/p/16385419.html