Nth catalan number

Recursion :

def findCatalan(n):
    def recur(n):
        if n == 0 or n == 1:
            return 1
        res = 0
        for i in range(n):
            res += recur(i) * recur(n-i-1)
        return res
    return recur(n)

Top down :

def findCatalan(n): 
    def top_down(n,dp):
        if dp[n] != -1:
            return dp[n]
        res = 0
        for i in range(n):
            res += top_down(i,dp) * top_down(n-i-1,dp)
        dp[n] = res
        return dp[n]
    
    dp = [-1] * (n+1)
    dp[0] = 1
    dp[1] = 1
    return top_down(n,dp)

Bottom Up:

def findCatalan(n): 
    def bottom_up(n,dp):
        for i in range(2,n+1):
            for j in range(i):
                dp[i]  += dp[j] * dp[i-j-1]
    
    dp = [0] * (n+1)
    dp[0] = 1
    dp[1] = 1
    bottom_up(n,dp) # Calling function
    return dp[n]

Source: practice.geeksforgeeks.org

Similar codes

5 votes284 views1 answer
Use time now to caculate execution time python
Python
0 vote192 views1 answer
Python operator overloading deal with type
Python
0 vote273 views1 answer
Pandas dataframe caption
Python
37 votes250 views6 answers
How to convert list into string in python
Python
0 vote264 views1 answer
Django-filter field name greater than
Python
0 vote204 views1 answer
Int' object is not subscriptable in python
Python
0 vote204 views1 answer
Python graphviz undirected graph
Python
0 vote223 views1 answer
Load py file converted from .ui file
Python
0 vote207 views1 answer
ModelCheckpoint
Python
-1 vote218 views1 answer
Randoomforest sklearn
Python