Poison

189. Rotate Array

发表于
Math
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class Solution {
    public void rotate(int[] nums, int k) {
        k %= nums.length;

        if (k == 0) {
            return;
        }

        for (int i = 0; i < getGreatestCommonDivisor(nums.length, k); i++) {
            int targetIndex = (i + k) % nums.length;
            while (targetIndex != i) {
                swap(nums, i, targetIndex);
                targetIndex = (targetIndex + k) % nums.length;
            }
        }
    }

    private int getGreatestCommonDivisor(int a, int b) {
        if (b == 0) {
            return a;
        }

        return getGreatestCommonDivisor(b, a % b);
    }

    private void swap(int[] nums, int i, int j) {
        int tmp = nums[i];
        nums[i] = nums[j];
        nums[j] = tmp;
    }
}

该方法完全是在草稿纸上找规律找出来的。

Reverse
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class Solution {
    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);
    }

    private void reverse(int[] nums, int i, int j) {
        while (i < j) {
            swap(nums, i, j);
            i++;
            j--;
        }
    }

    private void swap(int[] nums, int i, int j) {
        int tmp = nums[i];
        nums[i] = nums[j];
        nums[j] = tmp;
    }
}
Reference

189. Rotate Array