String, find the number of substrings

Given a string and a substring. The characters in the substring may be repeated.
The number of occurrences of the output substring.

Input description The length of
a string str and
a substring sub
str is greater than the length of sub

Output description
The number of occurrences of the output substring.

Input example 1
string = "today is nice. may nice day you have"
substring = "nice"

Output example 1
2

Input example 2
string = "abcabcabca"
substring = "abca"

Output example 2
3
question source: Niuke

Two layers of loops are used.
code show as below:

int find(const string &str, const string &sub){
    
    
    int len1=str.size();
    int len2=sub.size();
    int cnt=0;
    for(int i=0;i<len1;i++){
    
    
        int j=0,k=i;
        while(j<len2 && str[k++]==sub[j++]);
        if(j==len2)
            cnt++;
    }
    return cnt;
}