问题描述
#include <iostream>
using namespace std;
#include <vector>
int **function(vector<int> *nums,int rows){
int **output = new int*[3];
int index;
for (int i = 0; i < rows; i++){
for (int j = 0; j < 3; j++){
index = (3*i)+j;
output[i][j] = nums[index];
}
}
return output;
}
int main(void){
int array[3][3] = {{1,4,3},{4,2,6},{7,3,7}};
vector<int> nums;
for (int i = 0; i < 3; i++){
for (int j = 0; j < 3; j++){
nums.push_back(array[i][j]);
}
}
int **dbl = function(&nums,3);
for (int i = 0; i < 3; i++){
for (int j = 0; j < 3; j++){
cout << dbl[i][j] << " ";
}
cout << endl;
}
}
因此,我试图将2d数组放入向量中并将其放入双指针中,但是当我尝试使用索引取消引用nums时,出现从向量分配int的错误。不应自动取消引用向量吗?我无法用其他任何方式做到;这是使用向量的大型项目的一部分。
解决方法
您的函数function()
使用指向vector
(vector
的数组)的指针,但是您只有一个向量。
还要注意,rows
元素应该分配给output
而不是3
,并且应该为每行分配数组。
您想要的可能是这样:
#include <iostream>
using namespace std;
#include <vector>
int **function(const vector<int>& nums,int rows){ // use reference instead of pointer
int **output = new int*[rows]; // allocate rows elements
int index;
for (int i = 0; i < rows; i++){
output[i] = new int[3]; // allocate each row
for (int j = 0; j < 3; j++){
index = (3*i)+j;
output[i][j] = nums[index]; // now index applies to the vector instead of the pointer (array of vector)
}
}
return output;
}
int main(void){
int array[3][3] = {{1,4,3},{4,2,6},{7,3,7}};
vector<int> nums;
for (int i = 0; i < 3; i++){
for (int j = 0; j < 3; j++){
nums.push_back(array[i][j]);
}
}
int **dbl = function(nums,3); // don't use pointer: use reference instead
for (int i = 0; i < 3; i++){
for (int j = 0; j < 3; j++){
cout << dbl[i][j] << " ";
}
cout << endl;
}
}
如果要使用指向向量的指针,请先取消引用以访问向量的元素:
#include <iostream>
using namespace std;
#include <vector>
int **function(vector<int> *nums,int rows){
int **output = new int*[rows]; // allocate rows elements
int index;
for (int i = 0; i < rows; i++){
output[i] = new int[3]; // allocate each row
for (int j = 0; j < 3; j++){
index = (3*i)+j;
output[i][j] = (*nums)[index]; // dereference the pointer
// alternative way
// output[i][j] = nums->at(index);
}
}
return output;
}
int main(void){
int array[3][3] = {{1,7}};
vector<int> nums;
for (int i = 0; i < 3; i++){
for (int j = 0; j < 3; j++){
nums.push_back(array[i][j]);
}
}
int **dbl = function(&nums,3);
for (int i = 0; i < 3; i++){
for (int j = 0; j < 3; j++){
cout << dbl[i][j] << " ";
}
cout << endl;
}
}