I've been revising on my coding skills recently and then I made a program that outputs the contents of a multidimensional array. It is simple but when I experimented with the code this is what that happened:
int dv[3][3] {
{1,2,3},
{4,5,6},
{7,8,9}
};
for (auto col = dv; col != dv + 3; ++col) {
for (auto row = *dv; row != *col + 3; ++row) {
cout << *row << " ";
}
}
Output:
1 2 3 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9
Can anybody please tell me why is this happening?
Your error is inside the second loop initialization : auto row = *dv;. By doing so, you systematically come back to the beginning. Then, you go to *col + 3.
Look at it this way :
First loop turn :
col = dv;
row = *dv;
Prints each number until
row == *col + 3Output :
1 2 3
Second loop turn :
col = dv + 3;
row = *dv;
Prints each number until
row == *col + 3butcolisdv + 3Output :
1 2 3 4 5 6--> It started from the beginning (dv)
Total output with turn 1 and 2 : 1 2 3 1 2 3 4 5 6
for (auto col = dv; col != dv + 3; ++col) {
for (auto row = *col; row != *col + 3; ++row) { // (1)
cout << *row << " ";
}
}
// (1) : Starting at current `column` then printing until `column + 3`
Live example : https://ideone.com/Y0MKrW
dv is your dv variables. Its value is the memory address of your array int[3][3]. *dv is the address of the first array inside dv. Memory is contiguous so the address of the first array inside dv is the address of dv. To summarize : dv == *dv.*dv which is the address of the first array in dv. (*dv is strictly equal to dv[0]). Almost everything is about memory addesses, here.Your inner loop is starting at *dv. That is probably not what you meant to do.
