关于STL vector的遍历问题，请问怎样一边操作一边遍历删除？

#include
#include
#include
#include 
#include
using namespace std;
typedef struct rect
{
int id;
int length;
int width;
}Rect;
vector vec;
void * add(void *argc)

{ int i;
Rect r;
while(1){
sleep(1);
for(i=0;i<10;i++){
r.id=i;
r.length=i;
r.width=i;
vec.push_back(r);
}
}
return NULL;

}
void * delete4(void *argc){
while(1){
vector::iterator it=vec.begin();
for(it=vec.begin(); it!=vec.end();)
{
if(it->id== 4)
{
//将it赋值为erase()的返回值,它指向the new location of the element that followed the last element erased
vec.erase(it);
}
else
++it;
}
}
return NULL;
}
int main()
{ pthread_t tidp1;
pthread_t tidp2;
pthread_create(&tidp1,NULL,add,NULL);
pthread_create(&tidp2,NULL,delete4,NULL);
while(1){
sleep(2);
vector::iterator it=vec.begin();
for(it=vec.begin(); it!=vec.end(); ++it)
cout<id<<endl;

}
return 0;
}