如何在C++中删除动态数组的列

Question

I need help tring to delete columns of 2D array in C++. I've tried the operation by making a copy of the array. It succeeded only from the start to middle or the middle to the end of array. witch algorithm to jump unwanted columns in the array when making copy.

Answer 1

由于是动态数组，因此数组的变量是第一个值的指针，因此您无法获取大小，甚至无法使用 sizeof 来获取大小，但是在不知道大小的情况下使用动态数组是不可能的，无论是固定的还是在运行时抛出变量

Answer 2

This probably isn't the best way to do this but its' a potential solution

int removeColumn(int a){
vector<vector<int>> ret(M);
int i = 0;
for(vector<int> temp : Arr){
        vector<int> tempp(N-1);
        copy(temp.begin(), temp.begin()+a, tempp.begin());
        copy(temp.begin()+a+1,temp.end(),tempp.begin()+a);
        ret[i] = tempp;
        i++;
}
Arr = ret;
return 0;

}

Essentially you iterate over each row and use two copy statements to copy from the beginning to an index and from said index + 1 to the end. I'm sure there's a way to do this more elegantly, you could try looking at for_each loops however I doubt you could do it exclusively with copy. Tested it with this code.

https://repl.it/repls/PrettyTerrificOmnipage

Hope this helps