向量中的分段错误<vector<string> &gt; </vector<string>

Question

Why am I getting segmentation fault in this piece of code?

#include<bits/stdc++.h>
using namespace std;


int main()
{
    vector<vector<string> > v;
    v[0].push_back("good");
    
    cout<<v[0][0];

}

I am trying to insert the string "good" in the first vector, and I am trying to access that by v[0][0] , but it is giving me segmentation fault . Please help. Thanks.

Answer 1

The inner vector starts out with 0 elements, you push 1 element and then you can access the first via [0] . That's fine.

However, the outer vector works the same way: You first need to add an element before you can access it.

Either call the constructor that lets you specify the size:

vector<vector<string> > v(1);
v[0].push_back("good");

or push the element:

vector<vector<string> > v;
vector<string> w;
w.push_back("good");
v.push_back(w);