C中删除字符和字符串

/****删除字符****/

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<math.h>
#include<sys/types.h>

int main (void)
{
    char a[100];
    gets(a);
    char ch;
    scanf("%c",&ch);
    int i = 0,j = 0;
    while(a[i])
    {
        if( a[i] == ch)
        {
            j = i;
            while(a[j])
            {
                a[j] = a[j+1];
                j++;
            }
            i--;
        }
        i++;
    }
    puts(a);
    return 0;
}

/*******删除字符串*********/

int main ()
{
    char a[100];
    gets(a);
    char b[100];
    gets(b);
    int i = 0,j = 0,k;
    while(a[i])
    {
        if( a[i] == b[j])
        {
            k = i;
            while(b[j])
            {
                if(a[k] == b[j])
                {
                    k++;
                    j++;
                }
                else
                {
                    j = 0;
                    break;
                }
            }
            printf("-------------------------------\n");
            if( b[j] == '\0' )
            {
                printf("==========================\n");
                while(a[i])
                {
                    a[i++] = a[k++];
                }
                j = 0;
                i = 0;
            }
           
       
        }
        i++;
    }
   
    puts(a);
    return 0;
}