vector之assign

#include <iostream>
#include <vector>
using namespace std;
int main() {
	int n;
	vector<int> a,b(1),c(1);
	a.push_back(1);
	a.push_back(2);
	a.push_back(3);
	b[0]=66;
	c[0]=84;
	
	b.assign(a.begin(),a.end());//从size 1 到 size 3
	cout << b.size() << endl;//3
	for(int i=0;i<b.size();i++)
		cout << b[i] << endl;//123
		
	b.assign(c.begin(),c.end());//从size 3 到 size 1
	cout << b.size() << endl;//1
	for(int i=0;i<b.size();i++)
		cout << b[i] << endl;//84

	return 0;
}