vector insert segmentation fault second iteration - c++

Question

I'm actually trying to implement the floyd's warshall algorithm but I met a hard-point. I got a segmentation fault while i'm trying to find the shortest-way in my matrix of sequence. I follow this tutorial:
floyd's warshall algorithm
Everything work well except at the line 124:
chemin.insert(it,sequenceTest[v1-1][temp-1]);
where i get the segfault (You can skip the first part except if you want to know how I implement the algorithm butt the problem is in the second part):
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
int main()
{
int i,j,k;
int sequenceTest [4][4] = {{1,2,3,4},{1,2,3,4},{1,2,3,4},{1,2,3,4}};
int tempSequenceTest [4][4];
int distanceTest [4][4] = {{0,2,4,100000},{2,0,1,5},{4,1,0,3},{100000,5,3,0}};
int tempDistanceTest[4][4];
for(i=0;i<4;i++)
{
for(j=0;j<4;j++)
{
cout<<sequenceTest[i][j]<<" ";
}
cout<< endl;
}
cout<< endl;
for(i=0;i<4;i++)
{
for(j=0;j<4;j++)
{
cout << distanceTest[i][j] << " ";
}
cout<< endl;
}
cout<< endl;
for(k=0;k<3;k++)
{
cout <<endl;
for(i=0;i<4;i++)
{
for(j=0;j<4;j++)
{
cout << "i: " << i << " j: " << j << endl;
if(i == k)
{
tempSequenceTest[i][j] = sequenceTest[i][j];
tempDistanceTest[i][j] = distanceTest[i][j];
cout << " D " << tempDistanceTest[i][j] << " S " << tempSequenceTest[i][j];
}
if(j == k)
{
tempSequenceTest[i][j] = sequenceTest[i][j];
tempDistanceTest[i][j] = distanceTest[i][j];
cout << " D " << tempDistanceTest[i][j] << " S " << tempSequenceTest[i][j];
}
cout<< endl;
}
}
for(i=0;i<4;i++)
{
for(j=0;j<4;j++)
{
//cout<< "i: " << i << " j: " << j << " k:" << k << endl;
if(i!=k && j!=k)
{
if(distanceTest[i][j]> distanceTest[i][k] + distanceTest[k][j])
{
tempDistanceTest[i][j] = distanceTest[i][k] + distanceTest[k][j];
cout << distanceTest[i][j] << " > " << distanceTest[i][k] << " + " << distanceTest[k][j] << " = " << tempDistanceTest[i][j] << " " << i << j << endl;
tempSequenceTest[i][j] = k+1;
}
else
{
tempDistanceTest[i][j] = distanceTest[i][j];
tempSequenceTest[i][j] = sequenceTest[i][j];
}
}
}
}
cout<< endl;
for(i=0;i<4;i++)
{
for(j=0;j<4;j++)
{
distanceTest[i][j] = tempDistanceTest[i][j];
sequenceTest[i][j] = tempSequenceTest[i][j];
}
}
for(i=0;i<4;i++)
{
for(j=0;j<4;j++)
{
cout<<tempSequenceTest[i][j]<<" ";
}
cout<< endl;
}
cout<< endl;
for(i=0;i<4;i++)
{
for(j=0;j<4;j++)
{
cout << tempDistanceTest[i][j] << " ";
}
cout<< endl;
}
}
int v1, v2;
v1 = 1;
v2 = 4;
vector <int> chemin;
vector <int>::iterator it;
chemin.push_back(v1);
chemin.push_back(v2);
int temp = v2;
cout << sequenceTest[0][2];
while(sequenceTest[v1-1][temp-1] != v2)
{
it = chemin.begin() + 1;
cout << "V1: " << v1 << " V2: " << v2 << " Temp: " << temp << endl;
chemin.insert(it,sequenceTest[v1-1][temp-1]);
for(i=0;i<chemin.size();i++)
{
cout << chemin[i];
}
cout << endl;
temp = sequenceTest[v1-1][temp-1];
}
}
Thanks for your attention and for taking the time to help me!

Answer 1

chemin.insert(it,sequenceTest[v1-1][temp-1]);
This invalidates the iterator it, but you keep reusing it in the iterations that follow. If you want to continue inserting at the same position, capture the return value.
it = chemin.insert(it,sequenceTest[v1-1][temp-1]);