用递归实现字符串操作标准库函数

// StringAPI.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include<iostream>#include<math.h>#include<string.h>using namespace std;#define null NULLint strlen1(char *strDest);int strlen1(char* strDest){ return *strDest?1+strlen1(strDest+1):0;}int strlen2(char* p){if(*p)return 1+strlen2(p+1);elsereturn 0;}size_t _cdecl strlen3(char* strDest){char* start = strDest;while(*strDest++);return (int)(strDest - start-1);}//-----------------------------------------------int __cdecl strcmp ( const char * src, const char * dst ){ int ret = 0 ; while( ! (ret = *(unsigned char *)src - *(unsigned char *)dst) && *dst) ++src, ++dst; if ( ret < 0 ) ret = -1 ; else if ( ret > 0 ) ret = 1 ; return( ret );}int strcmp1(const char* src, const char* dst){int ret = 0;while(*src || *dst){int result = *src - *dst;if(result == 0){src++;dst++;continue;}if(result > 0){ret = 1;break;}else{ret = -1;break;}}return ret;}int strcmp2(const char* src, const char* dst){int result = *src - *dst;if(result == 0){return strcmp2(++src, ++dst);}if(result > 0)return 1;if(result < 0)return -1;}//------------------------------------------------------char * __cdecl strstr1(const char * str1, const char * str2)//首次匹配的子字符串的开始位置{ char *cp = (char *) str1; char *s1, *s2; if ( !*str2 ) return((char *)str1); while (*cp) { s1 = cp; s2 = (char *) str2; while ( *s1 && *s2 && !(*s1-*s2) ) s1++, s2++; if (!*s2) return(cp); cp++; } return(NULL);}char * _cdecl strstr2(const char* str1, const char* str2)//首次匹配的子字符串的最后位置{if(!*str2)return (char*)str1;if(!*str1)return NULL;int result = *str1 - *str2;if(result == 0)return strstr2(++str1, ++str2);elsereturn strstr2(++str1, str2);}//---------------------------------------------------------//Compare the first n chars of the two stringint __cdecl strncmp1(const char * first, const char * last, size_t count){ if (!count) return(0); while (--count && *first && *first == *last) { first++; last++; } return( *(unsigned char *)first - *(unsigned char *)last );}int _cdecl strncmp2(const char* first, const char* last, size_t count){while(--count && *first && !(*(first++) - *(last++)));return (*first - *last);}//-------------------------------------------char* strupr1(char* str){char* dst = str;char ret[10];int i = 0;int j = 0;int MIN = (int)'a';int MAX = (int)'z';while(*str && *str>=MIN && *str<=MAX){ret[i++] = (char)((int)(*(str+j++)) - 32);}strcpy(str, ret);return str;}char* strupr2(char* str){char* dst = str;char ret[10];return null;}//--------------------------------------------char * __cdecl strcat1 ( char * dst, const char * src ){ char * cp = dst; while( *cp ) cp++; /* find end of dst */ while( *cp++ = *src++ ) ; /* Copy src to end of dst */ return( dst ); /* return dst */}int _tmain(int argc, _TCHAR* argv[]){int _b;char a[10];a[0] = 'a';a[1] = 'b';//cout<<sizeof(a)<<endl;char *p = "hello";cout<<*(p+5)<<endl;cout<<strlen2(p)<<endl;cout<<strlen3(p)<<endl;cout<<strlen1(p)<<endl;cout<<strlen(p)<<endl;cout<<"***********************"<<endl;char * p1 = "52";char * p2 = "2131527";cout<<abs(*p1 - *p2)<<endl; //unsigned char的两个字符做减法运算，结果是正整数（ASCII的运算）cout<<strcmp(p1, p2)<<endl;cout<<strcmp1(p1, p2)<<endl;cout<<strcmp2(p1, p2)<<endl;cout<<"*********************"<<endl;char * c = strstr1(p2, p1);if(c != NULL)cout<<*strstr1(p2, p1)<<endl;cout<<*strstr2(p2, p1)<<endl;cout<<"***********************"<<endl;char * p3 = "2345";char * p4 = "23679";cout<<strncmp1(p3, p4, 3)<<endl;cout<<strncmp2(p3, p4, 3)<<endl;cout<<"************************"<<endl;char* p5 = "abc";//cout<<strupr1(p5)<<endl;cout<<p5<<endl;cout<<"strcpy()*********************************"<<endl;cout<<strcat(p1, p2)<<endl;int b;cin>>b;return 0;}