1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
|
// 386. Lexicographical Numbers
#include "leetcode.h"
/*
* given an integer 'n', return all the numbers in the range '[1, n]' sorted in
* lexicographical order. you must write an algorithm that runs in O(n) time
* complexity and uses O(1) extra space.
*/
int *lexicalOrder(int n, int *returnSize) {
int *ans = (int *)malloc(n * sizeof(int));
int curr = 1, k = 0;
for (int i = 0; i < n; i++) {
ans[i] = curr;
if (((curr << 3) + (curr << 1)) <= n)
curr = (curr << 3) + (curr << 1);
else {
if (curr >= n)
curr /= 10;
curr++;
while (!(curr % 10))
curr /= 10;
}
}
*returnSize = n;
return ans;
}
int main() {
int rs1, rs2;
int *lo1 = lexicalOrder(13, &rs1), *lo2 = lexicalOrder(2, &rs2);
for (int i = 0; i < rs1; i++)
printf("%d ", lo1[i]); // expect: [1,10,11,12,13,2,3,4,5,6,7,8,9]
printf("\n");
for (int i = 0; i < rs2; i++)
printf("%d ", lo2[i]); // expect: [1,2]
printf("\n");
free(lo1), free(lo2);
}
|