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.
题目分析
将整个数组向右移动k位，那么第i位的目标位置就是(i+k)%len
代码
class Solution {
public:
void rotate(vector<int>& nums, int k) {
vector<int> vec(nums);
int len=nums.size();
for(int i=0; i<len; i++) {
nums[(i+k)%len] = vec[i];
}
return ;
}
};
倒置的思路
将后k位倒置和前n-k位倒置，然后将整个数组倒置
class Solution
{
public:
void rotate(int nums[], int n, int k)
{
k = k%n;
// Reverse the first n - k numbers.
// Index i (0 <= i < n - k) becomes n - k - i.
reverse(nums, nums + n - k);
// Reverse tha last k numbers.
// Index n - k + i (0 <= i < k) becomes n - i.
reverse(nums + n - k, nums + n);
// Reverse all the numbers.
// Index i (0 <= i < n - k) becomes n - (n - k - i) = i + k.
// Index n - k + i (0 <= i < k) becomes n - (n - i) = i.
reverse(nums, nums + n);
}
};
