C语言中的字符串处理函数重写

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strcpy

#include<stdio.h>#include <string.h>char* strcpy2(char* str1,char*str2){    int n1,n2;    n1=sizeof(str1);    n2=sizeof(str2);    int i;    for(i=0;(i<n1 && str2[i]!='\0');i++)    {        str1[i]=str2[i];        printf("%s\n",str1);    }    if(n1>n2)    {        for(i=n1-n2;i<=n1;i++)        {            str1[i]='\0';            printf("%s\n",str1);        }    }}int main(){    char str1[5]="abc";    char str2[5]="123";    strcpy2(str1,str2);    printf("AAA:%s\n",str1);    char str3[5]="abc";    char str4[5]="123";    strcpy(str3,str4);    printf("BBB:%s\n",str3);}

strcat

#include <stdio.h>#include <string.h>char* strcat1(char*a,const char*b);int main(){    char a[100]="1234545";    char b[30]="sfjisdf";    char *c=strcat1(a,b);    printf("AAA:%s\n",c);    char d[100]="1234545";    char e[30]="sfjisdf";    char *f=strcat1(d,e);    printf("BBB:%s\n",f);    return 0;}char* strcat1(char*a,const char*b){    char*c=a;    while((a!=NULL)&&(b!=NULL))    {        while(*a)        {            a++;        }        while(*a++=*b++)        {            NULL;        }        return c;    }}

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