感谢各位了，我解决了，不过换了一个方法，代码如下

#include <iostream>
#include <stdio.h>
#include <string.h>
#define N 100005  
using namespace std;
char x[N];
int num[N];
int dum[N];
int solve(int length,int k){
//        printf("k==  %d;length== %d\n",k,length );

    int sum=0;
    num[length]+=k;
    for(int i=length;i>=0;i--){
        if(num[i]>9){
            num[i-1]++;
        }

    }

    for(int j=0;j<=length;j++){
        //            printf("aaalength== %d\n",sum);
        if(j==0){
            if(num[j]==10){
                sum+=1;
            }else{
                sum+=num[j];
            }
        }else{
            sum+=num[j]%10;
            num[j]=num[j]%10;
        }
        

//            printf("sum== %d\n",sum);
//            printf("num[%d]==  %d\n",j,num[j] );
    }
    return sum%10;
}
int main() {
    int t,sum,ans,i;
    scanf("%d",&t);
    while(t--){
        sum=0;
        scanf("%s",x);
        int len=strlen(x);
        for(i=0;i<len;i++){
            num[i]=x[i]-'0';
            dum[i]=x[i]-'0';
            sum+=num[i];
        }
        ans=sum%10;
        int j=num[len-1];
        if(len==1){
            printf("%d",19);

        }else{

            for(i=1;i<20;i++){
                if(solve(len-1,i)==0){
                    for(int j=0;j<len;j++){
                        printf("%d",num[j]);
                    }
               
                    break;
                }else{

                    for(int j=0;j<len;j++){
                        num[j]=dum[j];
                    }
                }

            }
        }
            printf("\n");
    }
//    system("pause");
    return 0;
}

调试时用的，提交时去了的