学到两个：

//ignore \n

cin.ignore();

//ignore a line

cin.ignore(1024, '\n'); 

#include<cstdio>
#include<iostream>
#include<string>
#include<algorithm>
#include<iterator>
#include<cstring>

//uva 10033 Problem G: Interpreter
#define ONLINE_JUDGE

using namespace std;
int regs[10];
int ram[1000];

int steps;
int pc=0;
int oper, arg1, arg2;

void load_ram()
{
    steps=0;
    pc=0;
    memset(regs, 0 ,sizeof(regs));
    memset(ram, 0 ,sizeof(ram));
    //string s;
    char s[5];
    int i=0;
    //for(int i=0;getline(cin, s)&&s.length();i++)
    for(int i=0;fgets(s, sizeof(s), stdin);i++)
    {
        if(s[0]=='\n')
        {
 //           printf("\\n \n");
            break;
        }
        //ram[i]=atoi(s.c_str());
        ram[i]=atoi(s);
#ifndef ONLINE_JUDGE
        cout<<ram[i]<<endl;
#endif
    }

}

void decode()
{
    oper=ram[pc]/100;
    arg1=ram[pc]/10%10;
    arg2=ram[pc]%10;
    pc++;

    steps++;
#ifndef ONLINE_JUDGE
    printf("steps %d pc %d: %d %d %d\n", steps, pc-1, oper, arg1, arg2);
#endif

}

void run()
{
    while(1)
    {
        decode();
        switch(oper)
        {
            //halt
            case 1:
                goto END;
                break;
            //2dn means set register d to n (between 0 and 9)
            case 2:
                regs[arg1]=arg2;
                break;
            //3dn means add n to register d
            case 3:
                regs[arg1]+=arg2;
                regs[arg1]%=1000;
                break;
            //4dn means multiply register d by n
            case 4:
                regs[arg1]*=arg2;
                regs[arg1]%=1000;
                break;
            //5ds means set register d to the value of register s
            case 5:
                regs[arg1]=regs[arg2];
                break;
            //6ds means add the value of register s to register d
            case 6:
                regs[arg1]+=regs[arg2];
                regs[arg1]%=1000;
                break;
            //7ds means multiply register d by the value of register s
            case 7:
                regs[arg1]*=regs[arg2];
                regs[arg1]%=1000;
                break;
            //8da means set register d to the value in RAM whose address is in register a
            case 8:
                regs[arg1]=ram[regs[arg2]];
                break;
            //9sa means set the value in RAM whose address is in register a to the value of register s
            case 9:
                ram[regs[arg2]]=regs[arg1];
                break;
            //0ds means goto the location in register d unless register s contains 0
            case 0:
                if(regs[arg2]!=0)
                    pc=regs[arg1];
                break;
            default:
                break;
        }

    }
END:
    return;

}


int main()
{
    int n;
    bool first=true;
    char instr[5]={0};
    //cin>>n;
    scanf("%d", &n);
    //ignore \n
    //cin.ignore();
    fgets(instr, sizeof(instr), stdin);
    memset(instr, 0, sizeof(instr));

    //ignore a line
    //cin.ignore(1024, '\n');
    fgets(instr, sizeof(instr), stdin);
    while(n-- >0)
    {
        load_ram();
        run();

        if(!first)
            printf("\n");
        printf("%d\n", steps);
        first=false;
    }


    return 0;
}