程序设计与算法（三）第五周测验(2018春季) 1:全面的MyString
题目网址：http://cxsjsxmooc.openjudge.cn/2018t3springw5/1/
【题目描述】
程序填空，输出指定结果
1 #include <cstdlib> 2 #include <iostream> 3 using namespace std; 4 int strlen(const char * s) 5 { int i = 0; 6 for(; s[i]; ++i); 7 return i; 8 } 9 void strcpy(char * d,const char * s) 10 { 11 int i = 0; 12 for( i = 0; s[i]; ++i) 13 d[i] = s[i]; 14 d[i] = 0; 15 16 } 17 int strcmp(const char * s1,const char * s2) 18 { 19 for(int i = 0; s1[i] && s2[i] ; ++i) { 20 if( s1[i] < s2[i] ) 21 return -1; 22 else if( s1[i] > s2[i]) 23 return 1; 24 } 25 return 0; 26 } 27 void strcat(char * d,const char * s) 28 { 29 int len = strlen(d); 30 strcpy(d+len,s); 31 } 32 class MyString 33 { 34 // 在此处补充你的代码 35 }; 36 37 38 int CompareString( const void * e1, const void * e2) 39 { 40 MyString * s1 = (MyString * ) e1; 41 MyString * s2 = (MyString * ) e2; 42 if( * s1 < *s2 ) 43 return -1; 44 else if( *s1 == *s2) 45 return 0; 46 else if( *s1 > *s2 ) 47 return 1; 48 } 49 int main() 50 { 51 MyString s1("abcd-"),s2,s3("efgh-"),s4(s1); 52 MyString SArray[4] = {"big","me","about","take"}; 53 cout << "1. " << s1 << s2 << s3<< s4<< endl; 54 s4 = s3; 55 s3 = s1 + s3; 56 cout << "2. " << s1 << endl; 57 cout << "3. " << s2 << endl; 58 cout << "4. " << s3 << endl; 59 cout << "5. " << s4 << endl; 60 cout << "6. " << s1[2] << endl; 61 s2 = s1; 62 s1 = "ijkl-"; 63 s1[2] = 'A' ; 64 cout << "7. " << s2 << endl; 65 cout << "8. " << s1 << endl; 66 s1 += "mnop"; 67 cout << "9. " << s1 << endl; 68 s4 = "qrst-" + s2; 69 cout << "10. " << s4 << endl; 70 s1 = s2 + s4 + " uvw " + "xyz"; 71 cout << "11. " << s1 << endl; 72 qsort(SArray,4,sizeof(MyString),CompareString); 73 for( int i = 0;i < 4;i ++ ) 74 cout << SArray[i] << endl; 75 //s1的从下标0开始长度为4的子串 76 cout << s1(0,4) << endl; 77 //s1的从下标5开始长度为10的子串 78 cout << s1(5,10) << endl; 79 return 0; 80 }
输入
无
输出
1. abcd-efgh-abcd- 2. abcd- 3. 4. abcd-efgh- 5. efgh- 6. c 7. abcd- 8. ijAl- 9. ijAl-mnop 10. qrst-abcd- 11. abcd-qrst-abcd- uvw xyz about big me take abcd qrst-abcd-
【题解】
1 class MyString 2 { 3 private: 4 char* p; 5 int len; 6 public: 7 MyString(const char* a){ 8 len=strlen(a); 9 p=new char[len+1]; 10 strcpy(p,a); 11 } 12 MyString(){ 13 len=1; 14 p=new char[1]; 15 strcpy(p,""); 16 } 17 MyString(const MyString& a){ 18 len=strlen(a.p); 19 p=new char[len+1]; 20 strcpy(p,a.p); 21 } 22 friend ostream& operator<<(ostream& o,const MyString& a){ 23 o<<a.p; 24 return o; 25 } 26 MyString& operator=(const MyString& a){ 27 if(p==a.p){ 28 return *this; 29 } 30 if(p) 31 delete p; 32 len=strlen(a.p); 33 p=new char[len+1]; 34 strcpy(p,a.p); 35 return *this; 36 } 37 char& operator[](int i){ 38 return p[i]; 39 } 40 friend MyString operator+(const MyString& a,const MyString& b){ 41 int l=b.len+a.len; 42 char *c=new char[l+1]; 43 strcpy(c,a.p); 44 int i ; 45 int j=0; 46 for( i = a.len; i<=l-1; ++i,++j) 47 c[i]=b.p[j]; 48 c[i] = 0; 49 return MyString(c); 50 } 51 void operator +=(const char *a){ 52 int i=len; 53 char *b=new char[len+1]; 54 strcpy(b,p); 55 delete p; 56 len=len+strlen(a); 57 p=new char[len+1]; 58 strcpy(p,b); 59 int j=0; 60 for(;i<=len-1;i++,j++){ 61 p[i]=a[j]; 62 } 63 p[i]=0; 64 } 65 friend bool operator<(const MyString& a,const MyString& b){ 66 if(strcmp(b.p,a.p)==1){ 67 return 1; 68 } 69 return 0; 70 } 71 friend bool operator>(const MyString& a,const MyString& b){ 72 if(strcmp(a.p,b.p)==1){ 73 return 1; 74 } 75 return 0; 76 } 77 friend bool operator==(const MyString& a,const MyString& b){ 78 if(strcmp(a.p,b.p)==0){ 79 return 1; 80 } 81 return 0; 82 } 83 char* operator()(int a,int l){ 84 char* c=new char[l+1]; 85 int j=0; 86 for(int i=a;i<a+l;i++,j++){ 87 c[j]=p[i]; 88 } 89 c[j]=0; 90 return c; 91 } 92 };
