Most efficient possible code for printing a specific board C++

Question

So I am trying to print a board exactly like this with the multidimensional array

char score[10][10] = {' '};

   a b c d e f g h i j
  +-------------------+
 0|                   |
 1|                   |
 2|                   |
 3|                   |
 4|                   |
 5|                   |
 6|                   |
 7|                   |
 8|                   |
 9|                   |
  +-------------------+

Currently this is my code:

#include <iostream>
using namespace std;
#include <vector>
#include <string.h>

int main() {
    char score[10][10] = {' '};

    cout << "   a b c d e f g h i j" << endl;
    cout << "  +-------------------+" << endl;

    for (int i = 0; i < 10; i++) {
        cout << " " << i << "|";
        for (int j = 0; j < 10; j++) {
            cout << score[i][j];
        }
        if(i == 0) {
            cout << "                  |";
        } else {
            cout << "                   |";
        }
        cout << endl;
    }
    cout << "  +-------------------+" << endl;
}

As you can see my code is inefficient and lengthy.

What would be the most efficient possible way ( or a more efficient way) of printing the board as exactly shown above with the multidimensional score array?

Answer 1

As the comments have pointed out, your code is almost efficient as possible. Making it shorter would do little to its run-time and instead obscure its meaning. There are however a few things you can do to speed it up.

1. Avoid an extra call to operator<<, evaluation of std::end, and unnecessary buffer flushes by using \n and including it in your existing string literals (evaluated at compile time).

2. Use printf instead of cout. See "performance" section of this article.

Answer 2

As already pointed out by others, there are not many ways to make this more efficient, particularly if constrained to use the cout stream.

But for the "lengthy" part, this is a few lines and characters shorter, albeit C++11:

cout << "   a b c d e f g h i j\n"
        "  +-------------------+\n";
for (int i = 0; i < 10; i++) {
    cout << ' ' << i << '|';
    for (char s : score[i])
      cout << s;
    cout << "         |\n";
}
cout << "  +-------------------+\n";

I don't understand why the spaces should be printed at the end instead of aligning the inner columns nicely, but I followed what you did in your code.

I have also got rid of the unnecessary endl which triggers stream flush and changed single letter strings to character constants, but I'm a bit doubtful of the resulting efficiency gain there. After all, it's just printing some output, not a time-critical computation task.

Answer 3

I'm going to assume that when you said you wanted to make it efficient and not lengthy what you really meant was that you wanted it to be correct and readable.

I don't believe what you currently have is "correct". I assume that char score[10][10] will contain a single printable character for each square of the board and perhaps a null character for cells where you don't want to print anything. And you want to print the contents of score into the template shown. As it stands, if you put anything other than a single space into char score[10][10] you will mess up your template.

As for readability, I think what you currently have is reasonably readable, perhaps it would benefit by having some functions extracted with meaningful names but that is just my personal preference. Based on my assumptions about what you were trying to do here is my corrected and refactored version:

#include <iostream>
#include <vector>
#include <string>

void printHeader() {
  std::cout << "   a b c d e f g h i j\n";
  std::cout << "  +-------------------+\n";
}

void printFooter() {
  std::cout << "  +-------------------+\n";
}

void printRowStart(int i) {
  std::cout << " " << i << "|";
}

void printRowEnd() {
  std::cout << "|\n";
}

void printSquare(char score) {
  char printable_score = (score != '\0') ? score : ' ';
  std::cout << printable_score;
}

void printRowScore(char (&row_score)[10]) {
  printSquare(row_score[0]);
  for (int i = 1; i != 10; ++i) {
    std::cout << " ";
    printSquare(row_score[i]);
  }
}

void printScore(char (&score)[10][10]) {
  printHeader();
  for (int i = 0; i != 10; ++i) {
    printRowStart(i);
    printRowScore(score[i]);
    printRowEnd();
  }
  printFooter();
}

int main(){
  char score[10][10] = { { 0 } };

  // Added to test assumed usage
  score[4][5] = 'x';
  score[4][6] = 'x';

  printScore(score);
}

You might also want to consider making the code print to a generic ostream to make it more testable.