标签：
Rotate an array of n elements to the right by k steps.
For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].
Note:
Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
Related problem: Reverse Words in a String II
[Solution]
先把A[k, n-1] 存储到临时空间， 移动A[0, k-1]。O（k）辅助存储
void rotate(vector<int>& nums, int k) { int n = nums.size(); if (n == 0 || k <= 0) return; k = k % n; vector<int> buf(k, 0); for (int i = 0; i < k; i++) buf[i] = nums[n - k + i]; for (int i = n - 1; i >= k; i--) nums[i] = nums[i - k]; for (int i = 0; i < k; i++) nums[i] = buf[i]; }
原地交换：
数组由AB两部分组成，移动k个位置形成BA
用r(A)表示A的逆序,则有r(r(A)) = A
r(AB)= r(B)r(A)
再将r(B), r(A)分别取逆得到BA
1 void rotate(vector<int>& nums, int k) 2 { 3 int n = nums.size(); 4 if (n == 0 || k <= 0) 5 return; 6 7 k = k % n; 8 reverse(nums, 0, n - 1); 9 reverse(nums, 0, k - 1); 10 reverse(nums, k, n - 1); 11 } 12 13 void reverse(vector<int>& nums, int s, int e) 14 { 15 for (int i = s, j = e; i < j; i++, j--) 16 swap(nums[i], nums[j]); 17 }
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原文地址：http://www.cnblogs.com/ym65536/p/4666278.html
