保留 3D 向量中的元素 c++

Question

I have a 3d container:

 std::vector<int, std::vector<std::vector<double>>> myVec;

that I want to have the dimensions [n+1][3*(n+10)+1][16*(n+10)+1]. I want to reserve this space in the vector quickly and without too many other spaghetti functions so I can emulate a dynamic 3D array. How would I do this?

Answer 1

Reserve or size?

http://www.cplusplus.com/reference/vector/vector/reserve/ http://www.cplusplus.com/reference/vector/vector/resize/

Demonstration of resize using constructor:

#include <iostream>
#include <vector>
using namespace std;

template <class T>
void printSize(T v) {
    cout<<v.size()<<endl;
}
int main(){
    int n = 1;//Initial n value;
    int d1 = n+1, d2 = 3+(n+10)+1, d3 = 16*(n+10)+1;
    vector<vector<vector<int>>> i3D(d1,vector<vector<int>>(d2,vector<int>(d3)));
    //i3D.resize(d1,vector<vector<int>>(d2,vector<int>(d3)));
    printSize(i3D);
    printSize(i3D[0]);
    printSize(i3D[0][0]);
    return 0;
}

In my example, I've resized using the constructor. You can do the same using the resize method.
Reserve on the other hand will require (that I know of) the use of loops and reserve memory per array (all).

Considered it to be a question of resize, because you indicated preset sizes for x, y, and z dimensions.