Leetcode 276. Paint Fence (经典DP)

 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.

Note:

n and k are non-negative integers. 

题解：经典DP; dp[i][0] 代表到i且最后一个元素不相邻 , dp[i][1] 代表到i且最后一个元素相邻。

class Solution {
public:
    int numWays(int n, int k) {
        if(n==0||k==0) return 0;
        if(n==1) return k;
        if(k==1) {
            if(n<=2) return 1;
            else return 0;
        }
        int adjacent=0,non_adjacent=k;
        int res=adjacent+non_adjacent;
        for(int i=2;i<=n;i++) {
            adjacent=non_adjacent;
            non_adjacent=res*(k-1);
            res=adjacent+non_adjacent;
        }
        return res;
    }
};