实现strlen,strcpy,strcat,strcmp同功能的函数stringLength,stringCopy,stringCatch,stringCompare

 #import <Foundation/Foundation.h>

 /*
     求字符串长度
  */
 int stringLength(char arr[]);

 /*
 复制字符串
  将arr1 复制到 arr
  */
 void stringCopy(char arr[],char arr1[]);

 /*
  拼接字符串
  将arr1 加到 arr 后
  */
 void stringCatch(char arr[],char arr1[]);

 /*
  比较字符串
  */
 int stringCompare(char arr[],char arr1[]);

 #import "FunctionOfArray.h"

 int stringLength(char arr[]){
     int length = ;
     while (arr[length] != '\0') {
         length++;
     }
     return length;
 }

 void stringCopy(char arr[],char arr1[]){
     int i = ;
     while (arr1[i] != '\0') {
         arr[i] = arr1[i];
         i++;
     }
     arr[i] = '\0';
 }

 void stringCatch(char arr[],char arr1[]){
     int k = stringLength(arr);
     int j = stringLength(arr1);
     for (int i = ; i < j; i++) {
         arr[k+i] = arr1[i];
     }
     arr[k + j] = '\0';
 }

 int stringCompare(char arr[],char arr1[]){
     int k = stringLength(arr);
     int j = stringLength(arr1);

     for (int i = ; i < k && i< j; i++) {
         if(arr[i] != arr1[i]){
             return (int)arr[i] - (int)arr1[i];
         }
     }
     if(k == j){
         return ;
     }else if(k > j ){
         return (int)arr[j] - (int)arr1[j];
     }else{
         return (int)arr[k] - (int)arr1[k];
     }
 }