Given integers n and k, find the lexicographically k-th smallest integer in the range from 1 to n.
Note: 1 ≤ k ≤ n ≤ 109.
Example:
Input:
n: 13 k: 2
Output:
10
Explanation:
The lexicographical order is [1, 10, 11, 12, 13, 2, 3, 4, 5, 6, 7, 8, 9], so the second smallest number is 10.
Solution:
class Solution {
public int findKthNumber(int n, int k) {
int result = 1;
for (k --; k > 0; ) {
int count = 0;
for (long first = result, last = first + 1; first <= n; first *= 10, last *= 10) {
count += (int) (Math.min(last, n + 1) - first);
}
if (k >= count) {
k -= count;
result ++;
} else {
k --;
result *= 10;
}
}
return result;
}
}