How to count certain word in string using C++ - c++

Question

How to counting the same word in a string
Input
Number of String
String1 = dadymathewdadreadad
String2 = sdgfghhjdjrjjyjjrtfdhe
Search = dad
Output
Number of dad in string1 = 3
Number of dad in string2 = 0
Code:
#include <iostream>
#include <string.h>
using namespace std;
int main() {
string str[50];
int n;
cin>>n;
for(int i = 0; i < n;i++) {
cin>>str[i];
}
for(int i = 0; i < 50;i++) {
if(substr(i,4) == "dad"){
n += 1;
}
}
cout<<n;
return 0;
}
ERROR
In function 'int main()':
[Error] 'substr' was not declared in this scope

Answer 1

One trick you could use here would be to just replace the search term (e.g. dad) with empty string, and then compare the length of the string before and after the replacement.
string input = "dadymathewdadreadady";
string search = "dad";
int size_orig = input.size();
replace(string, search, "");
cout << "number of 'dad' is: " << (size_orig - input.size()) / search.size();

Answer 2

You can use the find() member function of std::string, adjusting the start position after every successful find until the end of the string:
#include <string>
int count(const std::string& sentence, const std::string& word)
{
int total = 0;
size_t start = 0;
size_t pos = 0;
while ((pos = sentence.find(word, start)) != std::string::npos)
{
++total;
start = pos + word.size();
}
return total;
}
int main()
{
std::string input = "dadymathewdadreadady";
int c = count(input, "dad");
return 0;
}

Answer 3

Other Solution:
#include <iostream>
#include <string>
using namespace std;
int main(){
int n;
string s[50];
int c;
cin>>n;
for (int i=0;i<n;i++){
cin>>s[i];
}
for (int i=0;i<n;i++) {
c=0;
int found=s[i].find("jack");
while(found!=string::npos){
found=s[i].find("jack",found+1);
if(found) c++;
}
cout<<c<<endl;
}
}