In c++, we have function like strcmp(const char* c1,const char* c2) to help us decide which is alphabetically before the other. Yet we still want to use a more easy-going function as a bool operator < or something else like other logical operators.<\/p>\n
And here we have a customized user-define class String, which is incomplete due this is only for demonstration of overloading operators.<\/p>\n
\n#include <iostream>\n#include <iomanip>\nusing namespace std;\n\nclass String{\n\n\tchar* chars;\n\npublic:\n\n\tint length;\n\n\tString String::operator =(const char* r){\n\t\tlength=strlen(r);\n\t\tchars=(char*)malloc((length+1)*sizeof(char));\n\t\tfor(int i=0;i<=length;i++){\n\t\t\tthis->chars[i]=r[i];\n\t\t}\n\t\treturn *this;\n\t}\n\n\tString String::operator =(String r){\n\t\tlength=r.length;\n\t\tchars=(char*)malloc((length+1)*sizeof(char));\n\t\tfor(int i=0;i<=length;i++){\n\t\t\tthis->chars[i]=r[i];\n\t\t}\n\t\treturn *this;\n\t}\n\n\tchar &String::operator [](int idx){\n\t\treturn chars[idx];\n\t}\n\n\tbool operator <(String r)\n\t{\n\t\tfor(int idx=0;idx<=(length<r.length?length:r.length);idx++)\n\t\t{\n\t\t\tif(tolower(chars[idx])<tolower(r[idx]))\n\t\t\t\treturn true;\n\t\t\telse\n\t\t\t\tif(tolower(chars[idx])>tolower(r[idx]))\n\t\t\t\t\treturn false;\n\t\t\t\telse\n\t\t\t\t\tcontinue;\n\t\t}\n\t\treturn false;\n\t}\n\n\tbool operator >(String r)\n\t{\n\t\treturn r<*this;\n\t}\n\n\tbool operator ==(String r)\n\t{\n\t\treturn !(*this>r)&&!(*this<r);\n\t}\n\n\tbool operator !=(String r)\n\t{\n\t\treturn !(*this==r);\n\t}\n\n\tbool operator <=(String r)\n\t{\n\t\treturn !(*this>r);\n\t}\n\n\tbool operator >=(String r)\n\t{\n\t\treturn !(*this<r);\n\t}\n\n\tfriend ostream&operator <<(ostream &os,String &right);\n\n\tfriend istream&operator <<(istream &is,String &right);\n\n\tString(int n){\n\t\tlength=n;\n\t\tchars=new char[length];\n\t}\n\n\tString (){\n\t\tlength=0;\n\t}\n\n\tString (const char* cs){\n\t\t*this=cs;\n\t}\n\n};\n\nostream & operator<<(ostream &os, String &right)\n{\n\tfor(int i=0;i<=right.length;i++)\n\t{\n\t\tos<<right[i];\n\t}\n\n\treturn os;\n}\n\nistream & operator>>(istream &is,String &right)\n{\n\tint idx=2;\n\tchar* tmpcs=new char[idx];\n\tchar c;\n\tint i=0;\n\tfor(;;i++)\n\t{\n\t\tc=is.get();\n\t\tif(c!='n')\n\t\t{\n\t\t\tif(i>=idx)\n\t\t\t{\n\t\t\t\tidx=i+1;\n\t\t\t\ttmpcs=(char*)realloc(tmpcs,idx*sizeof(char));\n\t\t\t}\n\t\t\tif(isalpha(c))\n\t\t\t{\n\t\t\t\ttmpcs[i]=c;\n\t\t\t}\n\n\t\t}\n\t\telse\n\t\t{\n\t\t\tif(i>=idx)\n\t\t\t{\n\t\t\t\tidx=i+1;\n\t\t\t\ttmpcs=(char*)realloc(tmpcs,idx*sizeof(char));\n\t\t\t}\n\t\t\ttmpcs[i]='';\n\t\t\tbreak;\n\t\t}\n\t}\n\tright=tmpcs;\n\treturn is;\n\n}\n\ntemplate <typename T>\nvoid sort(T *source,int startidx,int endidx)\n{\n\tfor(int i=startidx+1;i<=endidx;i++)\n\t{\n\t\tfor(int j=startidx;j<i;j++)\n\t\t{\n\t\t\tif(source[i]<source[j])\n\t\t\t{\n\t\t\t\tT key=source[i];\n\t\t\t\tfor(int k=i;k>j;k--)\n\t\t\t\t{\n\t\t\t\t\tsource[k]=source[k-1];\n\t\t\t\t}\n\t\t\t\tsource[j]=key;\n\t\t\t\tbreak;\n\t\t\t}\n\t\t}\n\t}\n}\nint main()\n{\n\tString group[5];\n\n\tcout<<"Please input 5 words"<<endl;\n\tfor(int i=0;i<5;i++)\n\t{\n\t\tcin>>group[i];\n\t}\n\tsort(group,0,4);\n\tcout<<"after the sorting"<<endl;\n\tfor(int i=0;i<5;i++)\n\t{\n\t\tcout<<group[i]<<endl;\n\t}\n\tsystem("pause");\n\treturn 0;\n}\n<\/pre>\n","protected":false},"excerpt":{"rendered":"Overload the Logical Operators to Sort Strings Alphabetically In c++, we have function like strcmp(const char* c1,const char* c2) to help us decide which is alphabetically before the other. Yet we still want to use a more easy-going function as a bool operator < or something else like other logical operators. And here we have … <\/p>\n