[LintCode] Paint Fence 粉刷篱笆

There is a fence with n posts, each post can be painted with one of the k colors.
You have to paint all the posts such that no more than two adjacent fence posts have the same color.
Return the total number of ways you can paint the fence.

Notice

n and k are non-negative integers.

Example
Given n=3, k=2 return 6

post 1, post 2, post 3
way1 0 0 1
way2 0 1 0
way3 0 1 1
way4 1 0 0
way5 1 0 1
way6 1 1 0

LeetCode上的原题，请参见我之前的博客Paint Fence。

class Solution {
public:
    /**
     * @param n non-negative integer, n posts
     * @param k non-negative integer, k colors
     * @return an integer, the total number of ways
     */
    int numWays(int n, int k) {
        int same = 0, diff = k;
        for (int i = 2; i <= n; ++i) {
            int t = diff;
            diff = (same + diff) * (k - 1);
            same = t;
        }
        return same + diff;
    }
};