C++学习(13)
1 //字符串類的設計
2 //1.字符串類String能與C語言的字符串兼容使用
3 //2.重載邏輯等于運算符(==)
4 //3.字符串操作包括取字符串長度和取子串
5 #include<string.h>
6 #include<iostream.h>
7 #include<stdlib.h>
8 class String{
9 private:
10 char *str;
11 int size;
12 public:
13 // String();
14 String(char *s="");
15 String(const String &s);
16 ~String();
17
18 int Length()const;
19 String SubStr(int pos,int length);
20
21 String &operator=(const String &s);
22 String &operator=(char *s);
23
24 int operator==(const String &s)const;
25 int operator==(char *s)const;
26
27 friend int operator==(char *strL,const String &strR);
28 };
29
30 //String::String(){}
31 String::String(char *s){
32 this->size=strlen(s)+1;
33 str=new char[size];
34 strcpy(str,s);
35 }
36
37 String::String(const String &s){
38 this->size=s.size;
39 str=new char[size];
40 if(str==NULL){
41 exit(0);
42 }
43 for(int i=0;i<size;i++){
44 this->str[i]=s.str[i];
45 }
46 }
47
48 String::~String(){
49 delete []this->str;
50 }
51
52
53 int String::Length()const{
54 return this->size;
55 }
56
57 String String::SubStr(int pos,int length){
58 int charsLeft=size-pos-1;
59 String temp;
60 char *p,*q;
61
62 if(pos>=size-1){
63 return temp;
64 }
65 if(length>charsLeft){//長度不能超出范圍
66 length=charsLeft;
67 }
68 delete []temp.str;
69
70 temp.str=new char[length+1];
71
72 p=temp.str;
73 q=&this->str[pos];
74
75 for(int i=0;i<length;i++){
76 *p++=*q++;
77 }
78
79 *p=NULL;
80 temp.size=length+1;
81
82 return temp;
83 }
84
85 String &String::operator =(const String &s){
86 if(this->size!=s.size){
87 delete []str;
88 this->str=new char[s.size];
89 size=s.size;
90 }
91 for(int i=0;i<s.size;i++){
92 this->str[i]=s.str[i];
93 }
94 return *this;
95
96 }
97
98 String &String::operator=(char *s){
99 int length=strlen(s);
100 if(this->size!=length){
101 delete []this->str;
102 str=new char[length+1];
103 this->size=length+1;
104 }
105 strcpy(this->str,s);
106 return *this;
107 }
108
109 int String::operator==(const String &s)const{//String類和String類相比較
110 return strcmp(this->str,s.str)==0;
111 }
112 int String::operator==(char *s)const{//String類和C語言字符串比較
113 return strcmp(this->str,s)==0;
114 }
115
116 int operator==(char *strL,const String &strR){//C預壓字符串和String類比較
117 return strcmp(strL,strR.str)==0;
118 }
119
120 int main(){
121
122 String str1("Data Structure");
123 String str2("Structure");
124 String str3,str4,str5;
125
126 cout<<str1.Length()<<endl;
127
128 str3=str1.SubStr(5,9);
129 str4=str1.SubStr(5,9);
130 str5="Structure";
131
132 if(str3==str4){
133 cout<<"String和String字符串比較"<<endl;
134 }
135
136 if(str5=="Structure"){
137 cout<<"String和C語言字符串相比較"<<endl;
138 }
139 if("Strcture"==str2){
140 cout<<"C語言字符串和String相比較"<<endl;
141 }
142 return 0;
143 }
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轉載于:https://www.cnblogs.com/Tobi/p/9249788.html
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