60. Permutation Sequence
Explanation
To find the kth permutation sequence of numbers from 1 to n, we can follow these steps:
- Generate all permutations of numbers from 1 to n.
- Sort the permutations in lexicographical order.
- Return the kth permutation.
The time complexity of this approach is O(n!) as we are generating all permutations, and the space complexity is also O(n!) to store all permutations.
class Solution {
public String getPermutation(int n, int k) {
List<Integer> numbers = new ArrayList<>();
int[] factorial = new int[n + 1];
factorial[0] = 1;
for (int i = 1; i <= n; i++) {
numbers.add(i);
factorial[i] = factorial[i - 1] * i;
}
k--;
StringBuilder sb = new StringBuilder();
for (int i = 1; i <= n; i++) {
int index = k / factorial[n - i];
sb.append(numbers.get(index));
numbers.remove(index);
k -= index * factorial[n - i];
}
return sb.toString();
}
}Code Editor (Testing phase)
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