what can I get sum that string tokens converted int in C++? - c++

Question

I need to sum 100, 200, 300 in a.txt
a.txt
2323|A|5|0|2|100
2424|B|6|1|3|200
2525|C|7|2|4|300
so I opened this file, and read line by line using getline(), and tokenized.
main.cpp
for (std::string each; std::getline(split, each, split_char); tokens.push_back(each)) {
for (int i = 0; i < tokens.size(); i++) {
std::cout << tokens[i] << std::endl;
tokens.pop_back();
}
}
As expected, that code printed singly of all things.
so I thought using token index to sum values. but my code have error.
"vector subscript out of range" or no compile.
first try
for (std::string each; std::getline(split, each, split_char); tokens.push_back(each)) {
for (int i = 0; i < tokens.size(); i++) {
std::cout << tokens[i] << std::endl;
tokens.pop_back();
std::cout << tokens[5] << std::endl;
std::cout << tokens[11] << std::endl;
std::cout << tokens[17] << std::endl;
int a = 0;
int b = 0;
int c = 0;
int sum = 0;
a = stoi(tokens[5]);
b = stoi(tokens[11]);
c = stoi(tokens[17]);
sum = (a + b + c);
std::cout << sum << std::endl;
}
}
second try
for (std::string each; std::getline(split, each, split_char); tokens.push_back(each)) {
if(tokens.size() > 4) {
for (int k = 0; k < ((tokens.size() - 5) / 6) + 1; k++) {
int sum = 0;
int change = 0;
int j = 0;
j = 6 * k + 5;
change = stoi(tokens[j]);
sum += change;
std::cout << sum << std::endl;
tokens.pop_back();
}
}
}
what should I do sum value? and I'm wondering that tokens.size()`s meaning except meaning "size" because second for statement always get an error if not exactly correcting i < tokens.size()

Answer 1

You are modifying the tokens vector while you are looping through it. Don't do that. You are affecting its size(), which accounts for why you are able to go out of bounds.
You say that you need to sum only the last token of each line. But that is not what your code is trying to do. There is no need for an inner for loop at all. Simply split each line into a local tokens vector and then use tokens.back() to get the last token, eg:
std::string line;
int sum = 0;
while (std::getline(inFile, line))
{
std::istringstream iss(line);
std::vector<std::string> tokens;
std::string token;
while (std::getline(iss, token, '|')) {
tokens.push_back(token);
}
// use tokens as needed...
token = tokens.back();
sum += std::stoi(token);
}
std::cout << sum << std::endl;
Live Demo

Answer 2

I would like to structure my code slightly differently.
Rather than try and do everything in the main function split your code up so that you read each line and validate it is correct:
#include <iostream>
#include <string>
// A structure representing the data we want to parse.
struct DataLine
{
int v1;
char c;
int v2;
int v3;
int v4;
int v5;
// An input operator that will read one line of data.
// If the data is valid will update the variable we are reading into.
friend std::istream& operator>>(std::istream& str, DataLine& data)
{
DataLine tmp;
char s[5];
std::string extra;
if ( str >> tmp.v1 >> s[0] && s[0] == '|'
&& str >> tmp.c >> s[1] && s[1] == '|'
&& str >> tmp.v2 >> s[2] && s[2] == '|'
&& str >> tmp.v3 >> s[3] && s[3] == '|'
&& str >> tmp.v4 >> s[4] && s[4] == '|'
&& str >> tmp.v5
&& std::getline(str, extra) && extra.empty())
{
// all the data was read and the line was valid.
// update the correct variable.
swap(tmp, data);
}
else {
// there was an issue.
// set the stream to bad so that reading will stop.
str.setstate(std::ios::badbit);
}
return str;
}
// Standard swap method.
friend void swap(DataLine& lhs, DataLine& rhs) noexcept
{
using std::swap;
swap(lhs.v1, rhs.v1);
swap(lhs.c , rhs.c );
swap(lhs.v2, rhs.v2);
swap(lhs.v3, rhs.v3);
swap(lhs.v4, rhs.v4);
swap(lhs.v5, rhs.v5);
}
};
Then the loop you use to read the data becomes really trivial to implement.
int main()
{
DataLine data;
int sum = 0;
// Now we can read the data in a simple loop.
while(std::cin >> data) {
sum += data.v5;
}
std::cout << "Sum: " << sum << "\n";
}