72 lines
1017 B
C++
72 lines
1017 B
C++
#include <bits/stdc++.h>
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using namespace std;
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typedef long long ll;
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int first_digit(ll& n){
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int digits = (int)log10(n);
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n = (int)(n / pow(10, digits));
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return n;
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}
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void test_case(int tc){
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ll a, s;
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cin >> a >> s;
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ll b = 0;
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int bpow = 0;
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while(a > 0){
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if(s == 0){
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cout << -1 << '\n';
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return;
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}
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int la = a % 10, ls = s % 10;
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if(ls < la){
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ls = s % 100;
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s /= 10;
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}
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if(ls - la > 9 || la > ls){
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cout << -1 << '\n';
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return;
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}
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a /= 10;
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s /= 10;
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b += (ll)pow(10, bpow) * (ls - la);
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bpow++;
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}
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while(s > 0){
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b += (ll)pow(10, bpow) * (s % 10);
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s /= 10;
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bpow++;
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}
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cout << b << '\n';
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return;
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}
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int main(){
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ios::sync_with_stdio(0);
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cin.tie(0);
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int t;
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cin >> t;
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for(int tc = 1; tc <= t; ++tc){
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test_case(tc);
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}
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cout << flush;
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return 0;
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} |