不难，但有点繁琐

#include<bits/stdc++.h>
using namespace std;
int main()
{
	char c[20];
	cin>>c;
	int sum=0;
	sum=(c[0]-'0')*7+
	(c[1]-'0')*9+
	(c[2]-'0')*10+
	(c[3]-'0')*5+
	(c[4]-'0')*8+
	(c[5]-'0')*4+
	('1'-'0')*2+
	('9'-'0')*1+
	(c[6]-'0')*6+
	(c[7]-'0')*3+
	(c[8]-'0')*7+
	(c[9]-'0')*9+
	(c[10]-'0')*10+
	(c[11]-'0')*5+
	(c[12]-'0')*8+
	(c[13]-'0')*4+
	(c[14]-'0')*2;
	for(int i=0;i<=5;i++)
	cout<<c[i];
	cout<<"19";
	for(int i=6;i<strlen(c);i++)
	cout<<c[i];
	switch(sum%11)
	{
		case 0:cout<<"1";break;
		case 1:cout<<"0";break;
		case 2:cout<<"x";break;
		case 3:cout<<"9";break;
		case 4:cout<<"8";break;
		case 5:cout<<"7";break;
		case 6:cout<<"6";break;
		case 7:cout<<"5";break;
		case 8:cout<<"4";break;
		case 9:cout<<"3";break;
		case 10:cout<<"2";break;
	}
	cout<<endl;
    return 0;
}

注意事项:注意审题：假设所有要升级的身份证的四位年份都是19××年