08-Rotate-Array.md

Rotate Array

Problem Link

https://leetcode.com/problems/rotate-array/

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Pattern

• Array manipulation
• Reverse

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Approach

Rotate by reversing parts: reverse whole array, then reverse first k and last n-k segments (or use juggling algorithm).

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Time Complexity

O(n)

Space Complexity

O(1)

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Java Solution

class Solution {
    private void reverse(int[] a, int l, int r) {
        while (l < r) {
            int t = a[l]; a[l++] = a[r]; a[r--] = t;
        }
    }
    public void rotate(int[] nums, int k) {
        k %= nums.length;
        reverse(nums, 0, nums.length - 1);
        reverse(nums, 0, k - 1);
        reverse(nums, k, nums.length - 1);
    }
}