g2301_2400.s2318_number_of_distinct_roll_sequences.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g2301_2400.s2318_number_of_distinct_roll_sequences;

// #Hard #Dynamic_Programming #Memoization #2022_06_26_Time_254_ms_(91.67%)_Space_51.6_MB_(58.33%)

public class Solution {
    private int[][][] memo = new int[10001][7][7];
    private int mod = 1000000007;
    private int[][] m = {
        {1, 2, 3, 4, 5, 6},
        {2, 3, 4, 5, 6},
        {1, 3, 5},
        {1, 2, 4, 5},
        {1, 3, 5},
        {1, 2, 3, 4, 6},
        {1, 5}
    };

    public int distinctSequences(int n) {
        return dp(n, 0, 0);
    }

    private int dp(int n, int prev, int pprev) {
        if (n == 0) {
            return 1;
        }
        if (memo[n][prev][pprev] != 0) {
            return memo[n][prev][pprev];
        }
        int ans = 0;
        for (int x : m[prev]) {
            if (x != pprev) {
                ans = (ans + dp(n - 1, x, prev)) % mod;
            }
        }
        memo[n][prev][pprev] = ans;
        return ans;
    }
}