https://codeforces.com/problemset/problem/489/C
C. Given Length and Sum of Digits...
You have a positive integer m and a non-negative integer s. Your task is to find the smallest and the largest of the numbers that have length m and sum of digits s. The required numbers should be non-negative integers written in the decimal base without leading zeroes.
Input
The single line of the input contains a pair of integers m, s (1 ≤ m ≤ 100, 0 ≤ s ≤ 900) — the length and the sum of the digits of the required numbers.
Output
In the output print the pair of the required non-negative integer numbers — first the minimum possible number, then — the maximum possible number. If no numbers satisfying conditions required exist, print the pair of numbers "-1 -1" (without the quotes).
Examples
input
2 15
output
69 96
input
3 0
output
-1 -1
题意：
给定一个数m 和 一个长度s，计算最大和最小在s长度下的十进制各位数和为m的值
注意如果无法生成，即输出两个-1
题解：
有个小坑，在输出最大值时得注意下k 是否为 0
#include<bits/stdc++.h>
using namespace std;
int main()
{
int m, s, i, k;
cin >> m >> s;
if (s < 1 && m>1 || s > m * 9)
cout << -1 << " " << -1 << endl;
else {
for (i = m - 1, k = s; i >= 0; i--) {
int j = max(0, k - 9 * i);
if (j == 0 && i == m - 1 && k) j = 1;
cout << j;
k -= j;
}
cout << ' ';
for (i = m - 1, k = s; i >= 0; i--) {
int j = min(9, k);
cout << j;
k -= j;
}
}
}