在C++中使用嵌套向量

Question

我想实现一个vector<int>内部的vector<Type>C++中.但是每当我运行以下代码时,我都会收到错误信息

std::vector<std::vector<int> >::const_iterator’ has no member named ‘begin’
 std::vector<std::vector<int> >::const_iterator’ has no member named ‘end’

这是代码:

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>

using namespace std;

typedef vector<int> vector1D ;
typedef vector<vector1D > vector2D ;

void showarr(const vector2D& v)
{
    for (vector<vector1D >::const_iterator it1 = v.begin(); it1 != v.end(); ++it1) {
        for(vector<int>::const_iterator it2 = *it1.begin(); it2 != *it1.end(); ++it2) {
            cout<<*it2<<endl;
        }
    }
}
int main(int argc, char *argv[])
{
    int rownum;
    cin>>rownum;
    vector2D a;
    for ( int i = 0 ; i < rownum ; i++) {
        a.push_back(vector1D(rownum,0));
    }
    showarr(a);
    return 0;
}   

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Answer 1

尝试改变:

*it1.begin()

至

it1->begin()

Answer 2

它被解析为*(it1.begin()),而不是(*it1).begin().将其更改为it1->begin().