Removing trailing zeros in an array - c++

Question

I am trying to create a program that doesn't print the trailing zeros in an array.
My array size is 23. I am trying to start from the 23rd position in a for loop and end the for loop once a one is reached. Then I would only print up to that position. I have can't seem to get it right though. Can someone help me with this?
Thanks
void removeTrailZero(int array[]) {
int i = 0;
for (i = 23; array[i] == 0; i--) {
// printf("%d", i);
}
for (int x = 1; x < i + 1; x++) {
printf("%d",array[x]);
}
}

Answer 1

You can do something like this
for (i = 22; i >= 0; --i)
{
if (array[i] != 0)
break;
}
Then print your array between 0 and i (included)

Answer 2

Right now, your code looks like C, not C++. At least assuming the tag is correct and you really want to write C++ rather than C, I'd consider using some of the algorithms in the standard library to handle at least part of the job.
The standard library has an std::find_if to use for finding the value you care about. This works with iterators, not directly with the underlying storage. Since you want to start searching from the end, you can use a reverse_iterator to find the correct point:
auto last = std::find_if(std::crbegin(array), std::crend(array),
[](auto i) { return i != 0; });
When we print out the data, we want to iterate forward through the array from the beginning to that point--but that's a reverse_iterator, so we need to call its base() to get a forward iterator, and give that as the end of the range we want to print:
std::copy(std::cbegin(array), last.base(),
std::ostream_iterator<int>(std::cout, "\n"));

Answer 3

If You compile with C++14 -std=c++14 you can use the answer's #JerryCoffin:
#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <string>
template <std::size_t SIZE>
void removeTrailZero(const std::array<int, SIZE>& array) {
auto last = std::find_if(std::crbegin(array), std::crend(array),
[](auto i) { return i != 0; });
std::copy(std::cbegin(array), last.base(),
std::ostream_iterator<int>(std::cout, " "));
}
int main() {
std::array<int, 23> array1 = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0, 0, 0, 0, 0, 0, 0};
removeTrailZero(array1);
std::cout << std::endl;
std::array<int, 15> array2 = {1, 2, 3, 0, 0, 4, 5, 6, 0, 0, 0, 0, 0, 0};
removeTrailZero(array2);
std::cout << std::endl;
}
Output:
❯❯❯ g++ -std=c++14 ../test.cc -o test && ./test
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 0 0 4 5 6
For compiling with C++11 -std=c++11 you can use:
#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <string>
template <std::size_t SIZE>
void removeTrailZero(const std::array<int, SIZE>& array) {
auto last = std::find_if(array.crbegin(), array.crend(),
[](int i) { return i != 0; });
std::copy(array.cbegin(), last.base(),
std::ostream_iterator<int>(std::cout, " "));
}
int main() {
std::array<int, 23> array1 = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0, 0, 0, 0, 0, 0, 0};
removeTrailZero(array1);
std::cout << std::endl;
std::array<int, 15> array2 = {1, 2, 3, 0, 0, 4, 5, 6, 0, 0, 0, 0, 0, 0};
removeTrailZero(array2);
std::cout << std::endl;
}
Output:
❯❯❯ g++ -std=c++11 ../test.cc -o test && ./test
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 0 0 4 5 6
For older version of C++11, you can use:
#include <iostream>
void removeTrailZero(int array[]) {
int i = 22;
for (; i >= 0 && array[i] == 0; --i);
for (int j = 0; j <= i; ++j) {
std::cout << array[j] << " ";
}
}
int main() {
int array[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0, 0, 0, 0, 0, 0, 0};
removeTrailZero(array);
std::cout << std::endl;
int array2[] = {1, 2, 3, 0, 0, 4, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
removeTrailZero(array2);
std::cout << std::endl;
}
Output:
❯❯❯ g++ ../test.cc -o test && ./test
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 0 0 4 5 6
Note: For C++11 and C++14, removeTrailZero is a template function and can receive diferent sizes of std::array. For older version of C++11 removeTrailZerois design for receive a int[23].