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189. rotate array

admin 11月 15, 2020 0

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

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Input: [1,2,3,4,5,6,7] and k = 3
Output: [5,6,7,1,2,3,4]
Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]

Example 2:

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Input: [-1,-100,3,99] and k = 2
Output: [3,99,-1,-100]
Explanation: 
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

Note:

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class  {
    public void rotate(int[] nums, int k) {
         if (nums == null || nums.length == 0) return;
        int len = nums.length;
        k %= len;
        reverse(nums, 0, len - k - 1);
       reverse(nums, len - k, len - 1);
     reverse(nums, 0, len - 1);
    }

  private void reverse(int[] nums, int start, int end) {
     while (start < end) {
            int temp = nums[start];
         nums[start] = nums[end];
         nums[end] = temp;
            start++;
         end--;
       }
    }
}
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