HackerRank_Candies_C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
class Solution {
    public static int minCandies = 0;
    static void Main(String[] args) {
        int N = Convert.ToInt32(Console.ReadLine());
        int[] dp = new int[N];
        List<int> ratings = new List<int>();
        for(int i = 0; i < N; i++){
            ratings.Add(Convert.ToInt32(Console.ReadLine()));
        }
        double result = 0;
        bool isSorted = IsSorted(ratings);
        if(!isSorted){
            for(int j = 0; j < N; j++){
                dp[j] = -1;
            }
            for(int k = 0; k < N; k++){
                 GetMinCandies(k, ratings, ref dp);
            }
            result = dp.Sum();
        }
        else{
            double n = Convert.ToDouble(N);
            result = n * (n + 1) / 2;
        }
        Console.WriteLine(result);
    }
    
    public static int GetMinCandies(int start, List<int> ratings, ref int[] dp){
        if(start < 0 || start >= ratings.Count){
            return 0;
        }
        if(dp[start] == -1){
            if(start == 0){
                if(ratings[start + 1] >= ratings[start]){
                    dp[start] = 1;
                }
                else{
                     dp[start] = 1 + GetMinCandies(start + 1, ratings, ref dp);
                }
            }
            else if(start == (ratings.Count - 1)){
                if(ratings[start - 1] >= ratings[start]){
                    dp[start] = 1;
                }
                else{
                     dp[start] = 1 + GetMinCandies(start - 1, ratings, ref dp);
                }
            }
            else{
                if (ratings[start] <= ratings[start - 1] && ratings[start] <= ratings[start + 1])
                    {
                        dp[start] = 1;
                    }
                    else if (ratings[start] > ratings[start - 1] && ratings[start] <= ratings[start + 1])
                    {
                        dp[start] = GetMinCandies(start - 1, ratings, ref dp) + 1;
                    }
                    else if (ratings[start] <= ratings[start - 1] && ratings[start] > ratings[start + 1])
                    {
                        dp[start] = GetMinCandies(start + 1, ratings, ref dp) + 1;
                    }
                    else if(ratings[start] > ratings[start - 1] && ratings[start] > ratings[start + 1])
                    {
                        int u = GetMinCandies(start - 1, ratings, ref dp);
                        int v = GetMinCandies(start + 1, ratings, ref dp);
                        int max = u > v ? u : v;
                        dp[start] = max + 1;
                    }
            }
        }
        
        return dp[start];
    }
    public static bool IsSorted(List<int> sequence){
        int m = sequence[0];
        bool increasing = true;
        bool decreasing = true;
        for(int i = 1; i < sequence.Count; i++){
            if(sequence[i] > m){
                decreasing = false;
                m = sequence[i];
                continue;
            }
            if(sequence[i] < m){
                increasing = false;
                m = sequence[i];
                continue;
            }
            increasing = decreasing = false;
            break;
        }
        
        return increasing || decreasing;
    }
}