Counting occurrences of word in vector of characters - c++

Question

I have written a program to store a text file in vector of characters .
#include<iostream>
#include<fstream>
#include <algorithm>
#include<vector>
using namespace std;
int main()
{
vector<char> vec;
ifstream file("text.txt");
if(!file.eof() && !file.fail())
{
file.seekg(0, std::ios_base::end);
std::streampos fileSize = file.tellg();
vec.resize(fileSize);
file.seekg(0, std::ios_base::beg);
file.read(&vec[0], fileSize);
}
int c = count(vec.begin(), vec.end(), 'U');
cout << c;
return 0;
}
I want to count occurrence of "USER" in the text file , but using count i can only count number of characters . How can i count number of occurrences of "USER" in the vector of character?
For example
text.txt
USERABRUSER#$$* 34 USER ABC RR IERUSER
Then the count of "USER" is 4. Words can only be in uppercase.

Answer 1

std::string has a find member function that will find an occurrence of one string inside another. You can use that to count occurrences something like this:
size_t count(std::string const &haystack, std::string const &needle) {
auto occurrences = 0;
auto len = needle.size();
auto pos = 0;
while (std::string::npos != (pos = haystack.find(needle, pos))) {
++occurrences;
pos += len;
}
return occurrences;
}
For example:
int main() {
std::string input{ "USERABRUSER#$$* 34 USER ABC RR IERUSER" };
std::cout << count(input, "USER");
}
...produces an output of 4.

Answer 2

This is how I would do it:
#include <fstream>
#include <sstream>
#include <iostream>
#include <unordered_map>
#include <string>
using namespace std;
int main() {
unordered_map<string, size_t> data;
string line;
ifstream file("text.txt");
while (getline(file, line)) {
istringstream is(line);
string word;
while (is >> word) {
++data[word];
}
}
cout << data["USER"] << endl;
return 0;
}

Answer 3

Let's try again. Once again, a vector isn't necessary. This is what I would consider to be the most C++ idiomatic way. It uses std::string's find() method to repeatedly find the substring in order until the end of the string is reached.
#include <fstream>
#include <iostream>
#include <string>
int main() {
// Read entire file into a single string.
std::ifstream file_stream("text.txt");
std::string file_contents(std::istreambuf_iterator<char>(file_stream),
std::istreambuf_iterator<char>());
unsigned count = 0;
std::string substr = "USER";
for (size_t i = file_contents.find(substr); i != std::string::npos;
i = str.find(substr, i + substr.length())) {
++count;
}
}