[C] Remove all the occurrences in String 1 of String 2 w/o any Library Function

/*******************************************************************************

    Remove all the occurrences of string 2 from string 1. For example -
    ------Input
    string 1 : abcxyababccz
    string 2 : abc
    ------Output
    xyz
    length: 3

*******************************************************************************/

#include <stdio.h>

// Function to find string length
int length(char str[])
{
    int len;
    for(len=0; str[len]!='\0'; len++);
    return len;
}

// Recursively removing string2 from string1
void removeOccurrence(char str[], int i, int n)
{
    str[i] = str[i+n];

    if(str[i+n]=='\0')
        return;
    removeOccurrence(str, i+1, n);
}

// function to find all the occurrences of string 2 in string 1
void findOccurrence(char s1[], char s2[], int n1, int n2)
{
    int i=0, j=1, flag, pos;
    while(i<n1)
    {
        /*
            break if length to be compared of string 1 is
            < the length of s2
        */
        if(n1-i < n2)
            break;

        if(s1[i]==s2[0])
        {
            flag = 0;
            for(j=1; j<n2; j++)
            {
                if(s1[i+j]!=s2[j])
                {
                    flag = 1;
                    pos = j;    // storing the position where string didnt match
                    break;
                }
            }
            // if flag is zero then s2 was found in s1 so remove it
            if(flag==0)
            {
                removeOccurrence(s1, i, n2);
                n1 = length(s1);            // Updating the length of string 1
                i = 0;
            }
            else        // s2 was not found in s1
                i += pos;
        }
        else
            i++;
    }
}


void main()
{
    char str1[100], str2[100];
    int n1, n2;

    printf("Maximum String Length is 100!!!\n");
    printf("Enter String 1: ");
    gets(str1);
    printf("Enter String 2: ");
    gets(str2);

    n1 = length(str1);
    n2 = length(str2);
    // if n2 is greater then n1 cannot have occurrences of n2 in it
    if(n1>n2)
    {
        findOccurrence(str1, str2, n1, n2);
        printf("After removing Occurrences of String 2 from String 1\n");
        n1 = length(str1);
        printf("%s", str1);
        printf("\nLength: %d", n1);
    }
    else
        printf("Length of string 2 cannot be greater than that of String 1!\n");
}