索引 2D 向量时'Reference to type const..'编译错误

'Reference to type const..' compile error while indexing 2d vector

本文关键字：type const 编译 错误 to Reference 向量 2D 索引      更新时间：2023-10-16

当我将元素推送到另一个向量内的向量时，我收到编译错误。

void addElem(vector<vector<int> >& subsets, int elem){
int smallerSubsetSize = subsets.size();
for(int i = 0; i < smallerSubsetSize; i++){
vector<int> originalSubset = subsets[i];
subsets.push_back(originalSubset.push_back(elem));
}
vector<int> uniset;
uniset.push_back(elem);
subsets.push_back(uniset);
}

我收到以下错误：

powerset.cpp:11:27: error: reference to type 'const
std::__1::__vector_base<std::__1::vector<int, std::__1::allocator<int> >,
std::__1::allocator<std::__1::vector<int, std::__1::allocator<int> > >
>::value_type' (aka 'const std::__1::vector<int, std::__1::allocator<int> >')
could not bind to an rvalue of type 'void'
subsets.push_back(originalSubset.push_back(elem));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:688:62: note: passing
argument to parameter '__x' here
_LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
^
1 error generated.

我无法理解编译器想说什么。我尝试按值传递向量以及仅将代码放在 main 中。

这是我的完整代码，以防万一很重要：

// CtCI 8.4
#include <iostream>
#include <vector>
using namespace std;
void addElem(vector<vector<int> >& subsets, int elem){
int smallerSubsetSize = subsets.size();
for(int i = 0; i < smallerSubsetSize; i++){
vector<int> originalSubset = subsets[i];
subsets.push_back(originalSubset.push_back(elem));
}
vector<int> uniset;
uniset.push_back(elem);
subsets.push_back(uniset);
}
void printVector(const vector<int> &v){
for(int i = 0; i < v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
}
int main(){
// set size
int n;
cin >> n;
vector<int> set(n);
for(int i = 0; i < n; i++){
cin >> set[i];
}
vector<vector<int> > subsets;
for(int i = 0; i < set.size(); i++){
addElem(subsets, set[i]);
}
// print subsets
for(int i = 0; i < subsets.size(); i++){
printVector(subsets[i]);
}
}

void addElem(vector<vector<int> >& subsets, int elem){
int smallerSubsetSize = subsets.size();
vector<int> originalSubset;
for(int i = 0; i < smallerSubsetSize; i++)
{
originalSubset = subsets[i];
originalSubset.push_back(elem);
subsets.push_back(originalSubset); 
/*by doing this, we are passing vectortype as argument to push_back(),
do not pass argument in push_back() as void,   
as originalSubset.push_back(elem) return void as return type */
} 
vector<int> uniset;
uniset.push_back(elem);
subsets.push_back(uniset);
}

参考： http://www.cplusplus.com/reference/vector/vector/push_back/

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