矢量迭代器不兼容(运行时错误）

我收到一个运行时错误，说向量迭代器不兼容。

#include <iostream>
#include <vector>
using namespace std;

struct Interval
{
public:
    Interval(int s,int e):start(s),end(e) {}
    int start;
    int end;
};

void merge_intervals(vector<Interval>& Interval1, vector<Interval>& Interval2, vector<Interval>& merged)
{
    int i = 0 ;
    cout<<"i"<<i<<endl;
    vector<Interval>::iterator it1 = Interval1.begin();
    vector<Interval>::iterator it2 = Interval2.begin() ;
    while(it1 != Interval1.end() && it2 !=Interval1.end())
    {
        cout<<"i"<<i<<endl;
        i++;
        if(it1->start <= it2->start)
        {
            if(it1->end <= it2->end)
            {
                it1++;
                merged.push_back(*it1);
            }
            else
            {
                it1++;
                it2++;
                merged.push_back(Interval(it1->start,it2->end));
            }
        }
        else
        {
            if(it1->end >= it2->end)
            {
                it2++;
                merged.push_back(*it2);
            }
            else
            {
                it1++;
                it2++;
                merged.push_back(Interval(it2->start,it1->end));
            }
        }
        while(it1 != Interval1.end())
        {
            merged.push_back(*it1);
            *it1++;
        }
        while(it2 != Interval2.end())
        {
            merged.push_back(*it2);
            *it2++;
        }
    }
}
void print_intervals(vector<Interval>& merged)
{
    vector<Interval>::iterator  it = merged.begin();
    for(it = merged.begin();it != merged.end(); ++it)
    {
        cout<<"("<<it->start<<","<<it->end<<")"<<endl;
    }
}
void test1()
{
    vector<Interval> Interval1, Interval2, merged ;
    Interval1.push_back(Interval(1,4));
    Interval1.push_back(Interval(6,10));
    Interval1.push_back(Interval(14,19));
    Interval2.push_back(Interval(13,17));
    merge_intervals(Interval1, Interval2, merged);
    print_intervals(merged);
}
int main()
{
    test1();
    return 0;
}