如何对齐不同长度的输出C ++

Question

I have tried to search many post on this, and I still cant figure this out. say I have a loop where it reads lines from a text file and then displays them on the screen. I want each peice of data to be aligned, but the problem is the data can be diferent legnths so using a static value in setw is not working. for example here is a text file

000000  apples      pears     2.00
000001  oranges     bannana   1.00

this is how I want it to look on the screen, but my screen looks like this

000000  apples      pears     2.00
000001 oranges    banana   1.00

it is seeing that oranges is 1 longer than apples and then it is moving it over 1 to the left. it does the same thing with banana and pears

how do I align it like the first example(which is how it looks in my text file)

this is what I am using:

cout << account << setw(10) << fruit << setw(10) << fruit2 << setw(10) << money << endl;

I feel like the setw(10) needs to be non static. I have also tried left right and that does not work either.

Answer 1

Here is how I solved this problem, if you are using std::string:

cout << left << setw(10) << account << setw(10) << fruit << setw(10 + strlen(fruit2.c_str()) -  strlen(fruit.c_str())) << fruit2 << endl;   

It takes the length of the string into account with the formatting. You can choose an arbitrary offset as long as the fruit names don't get too long ("strawberries" in place of "apples" breaks the format with

setw(10)

Answer 2

This makes little or no sense--if you're really getting that result, it sounds like a problem with your compiler. I wrote a quite demo, similar to what you have in the question:

#include <iostream>
#include <iomanip>
#include <string>
#include <iterator>

struct account {
    std::string acct;
    std::string fruit;
    std::string fruit2;
    double qty;

    friend std::ostream &operator<<(std::ostream &os, account const &a) {
        return os << a.acct << std::setw(10) 
                << a.fruit << std::setw(10)
                << a.fruit2 << std::setw(5)
                << a.qty;
    }   
};

int main() { 
    account accts[] = {
        { "0000", "apples", "pears", 2.0 },
        { "0001", "oranges", "banana", 1.0 }
    };

    std::copy_n(accts, 2, std::ostream_iterator<account>(std::cout, "\n"));
}

The result is produced is aligned as anybody who understood setw would expect:

0000    apples     pears    2
0001   oranges    banana    1

Each item is right-aligned in its field, just as you'd expect from the specification.

Answer 3

You're simply missing the std::ios_base::left flag.

std::cout << std::setw(10) << std::setiosflags(std::ios_base::left)
      << "x" << "y" << std::endl;