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Count ways to reach the n'th stair

Sumit Rawal answered on October 19, 2022 Popularity 8/10 Helpfulness 2/10

answer Count ways to reach the n'th stair

Count ways to reach the n'th stair

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class Solution
{
    //Function to count number of ways to reach the nth stair.
    int mod = 1000000007;
    
    int countWays(int n)
    {
        int[] dp = new int[n];
        Arrays.fill(dp, -1);
        
        return helper(n, 0, dp); 
    }
    
    int helper(int n, int current, int[] dp) {
        
        if (current > n)
            return 0;
            
        if (current == n)
            return 1;
            
        if (dp[current] != -1)
            return dp[current];
            
        return dp[current] = (helper(n, current + 1, dp) + helper(n, current + 2, dp))%mod; 
        
    }
}

Popularity 8/10 Helpfulness 2/10 Language whatever

Source: Grepper

Tags: count whatever

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Contributed on Oct 19 2022

Sumit Rawal

0 Answers Avg Quality 2/10

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