删除一个字符串中的数字(C语言)

# include <stdio.h>
#include <stdlib.h>
void DropNum(char* str){
int i=0;
int j=0;
while(str[i]!='\0'){
if(str[i]>'9'||str[i]<'0')
str[j++]=str[i];
i++;
}
str[j]='\0';//字符串最后一个字符时'\0'
}
void main(){
char ch[] = "abcd123efg456hijk";
    DropNum(ch);
printf("%s\n",ch);
}