c语言基础，周六复习

今天将一周所学的C基础从头梳理了一般，并完成了作业：

• strlen:

#include<stdio.h>
#include<string.h>
int mylen(char *p){
//  char *pa = p;
    int len = 0;
    while(*p != '\0'){
        len++;
        p++;
    }
    return len-1;
}
int main(){
     char arr[32] = {'\0'};
     printf("input string:");
     fgets(arr,32,stdin);
     int str_len = mylen(arr);
     printf("str_len = %d\n",str_len);

     //printf("strlen(arr) = %d\n",(int)strlen(arr));
     return 0;
}

• strcpy:

#include<stdio.h>
#include<string.h>
char* mycpy(char *p1,char *p2){
    return p2;
}
int main(int argc,char *argv[]){
    char arr[32] = {'\0'};
    char buf[32] = {'\0'};
    printf("input first string:");
    fgets(arr,32,stdin);
    printf("input second string:");
    fgets(buf,32,stdin);
    printf("%s\n",mycpy(arr,buf));
    printf("%s\n",strcpy(arr,buf));
    return 0;
}

• strcmp:

#include<stdio.h>
#include<string.h>
/******************自制实现比较字符串的功能******************/
int mycmp(char *p1,char *p2){
    int count=0;
    int return_i;
    while(*p1 == *p2){                   //判断字符串是否相等
        p1++;
        p2++;
        if(*p1==10 && *p2==10)  {
            count++;
            break;
        }
    }
    if(count==1)
        return 0;
    else{
        return_i=*p1-*p2;              //不相等时，判断返回值
        if(*p1==10 || *p2==10)
            return_i = *p1-*p2;
        return return_i;
    }
}
int main(int argc,char *argv[]){
    char arr[32] = {'\0'};
    char buf[32] = {'\0'};
    printf("input first array:");
    fgets(arr,32,stdin);
    printf("input second array:");
    fgets(buf,32,stdin);
    int i = mycmp(arr,buf);          //主函数进行调用
    printf("%d\n",i);
    printf("%d\n",strcmp(arr,buf));
    return 0;
}

• strcat:

#include<stdio.h>
#include<string.h>
char *mycat(char *p1,char *p2){
    char arr_p[32] = {0};
    char *p = arr_p;
    while(*p1 != '\0'){
        *p = *p1;
        p1++;
        p++;
    }
    while(*p2 != '\0'){
        *p = *p2;
        p2++;
        p++;
    }
    return arr_p;
}
int main(int argc,char argv[]){
    char arr[32] = {'\0'};
    char buf[32] = {'\0'};
    printf("input frist string:\n");
    fgets(arr,32,stdin);
    printf("input srcond string:\n");
    fgets(buf,32,stdin);
    printf("%s\n",mycat(arr,buf));
//  printf("%s\n",strcat(arr,buf));
}