CF1835A k-th equality
我们考虑因为题目上说：
Each input file has at most \(5\) test cases which do not satisfy \(A,B,C \leq 3\).
不满足 \(A,B,C \leq 3\) 的数据最多只有 \(5\) 组
所以说，我们可以枚举所有的 \(A\) 位数，然后每次减去可能的 \(B\) 位数的个数即可。
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int NN = 10;
int t,a,b,c;
ll k;
ll l[NN] = {0,1,10,100,1000,10000,100000,1000000};
ll r[NN] = {0,9,99,999,9999,99999,999999,9999999};
int main(){
scanf("%d",&t);
while(t--){
scanf("%d %d %d %lld",&a,&b,&c,&k);
if(c != max(a,b) && c != max(a,b)+1) {puts("-1");continue;}
ll ans = k;
for(ll i = l[a]; i <= r[a]; ++i){
ll lt = max(l[b],l[c] - i),rt = min(r[b],r[c] - i);
if(lt > rt) rt = lt - 1;
if(ans <= (rt - lt + 1)){
printf("%lld + %lld = %lld\n",i,lt + ans - 1,(i + lt + ans - 1));
ans = 0;
break;
}
ans -= (rt - lt + 1);
}
if(ans > 0) puts("-1");
}
}