PAINTING-FENCE-ALGORITHM

#include <bits/stdc++.h>
using namespace std;
 
long countWays(int n, int k) {
    long dp[n + 1];
    memset(dp, 0, sizeof(dp));
    long long mod = 1000000007;
 
    dp[1] = k;
    dp[2] = k * k;
 
    for (int i = 3; i <= n; i++) {
        dp[i] = ((k - 1) * (dp[i - 1] + dp[i - 2])) % mod;
    }
 
    return dp[n];
}
 
int main() {
    int n = 3, k = 2;
    cout << countWays(n, k) << endl;
    return 0;
}