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Python3 program for Shannon Fano Algorithm

Jealous Jellyfish answered on September 18, 2023 Popularity 2/10 Helpfulness 1/10

answer Python3 program for Shannon Fano Algorithm

Python3 program for Shannon Fano Algorithm

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# Python3 program for Shannon Fano Algorithm
 
 
# declare structure node
class  node :
    def __init__(self) -> None:
        # for storing symbol
        self.sym=''
        # for storing probability or frequency
        self.pro=0.0
        self.arr=[0]*20
        self.top=0
p=[node() for _ in range(20)]
 
# function to find shannon code
def shannon(l, h, p):
    pack1 = 0; pack2 = 0; diff1 = 0; diff2 = 0
    if ((l + 1) == h or l == h or l > h) :
        if (l == h or l > h):
            return
        p[h].top+=1
        p[h].arr[(p[h].top)] = 0
        p[l].top+=1
        p[l].arr[(p[l].top)] = 1
         
        return
     
    else :
        for i in range(l,h):
            pack1 = pack1 + p[i].pro
        pack2 = pack2 + p[h].pro
        diff1 = pack1 - pack2
        if (diff1 < 0):
            diff1 = diff1 * -1
        j = 2
        while (j != h - l + 1) :
            k = h - j
            pack1 = pack2 = 0
            for i in range(l, k+1):
                pack1 = pack1 + p[i].pro
            for i in range(h,k,-1):
                pack2 = pack2 + p[i].pro
            diff2 = pack1 - pack2
            if (diff2 < 0):
                diff2 = diff2 * -1
            if (diff2 >= diff1):
                break
            diff1 = diff2
            j+=1
         
        k+=1
        for i in range(l,k+1):
            p[i].top+=1
            p[i].arr[(p[i].top)] = 1
             
        for i in range(k + 1,h+1):
            p[i].top+=1
            p[i].arr[(p[i].top)] = 0
             
 
        # Invoke shannon function
        shannon(l, k, p)
        shannon(k + 1, h, p)
     
 
 
# Function to sort the symbols
# based on their probability or frequency
def sortByProbability(n, p):
    temp=node()
    for j in range(1,n) :
        for i in range(n - 1) :
            if ((p[i].pro) > (p[i + 1].pro)) :
                temp.pro = p[i].pro
                temp.sym = p[i].sym
 
                p[i].pro = p[i + 1].pro
                p[i].sym = p[i + 1].sym
 
                p[i + 1].pro = temp.pro
                p[i + 1].sym = temp.sym
             
         
     
 
 
# function to display shannon codes
def display(n, p):
    print("\n\n\n\tSymbol\tProbability\tCode",end='')
    for i in range(n - 1,-1,-1):
        print("\n\t", p[i].sym, "\t\t", p[i].pro,"\t",end='')
        for j in range(p[i].top+1):
            print(p[i].arr[j],end='')
     
 
 
# Driver code
if __name__ == '__main__':
    total = 0
 
    # Input number of symbols
    print("Enter number of symbols\t: ",end='')
    n = 5
    print(n)
    i=0
    # Input symbols
    for i in range(n):
        print("Enter symbol", i + 1," : ",end="")
        ch = chr(65 + i)
        print(ch)
 
        # Insert the symbol to node
        p[i].sym += ch
     
 
    # Input probability of symbols
    x = [0.22, 0.28, 0.15, 0.30, 0.05]
    for i in range(n):
        print("\nEnter probability of", p[i].sym, ": ",end="")
        print(x[i])
 
        # Insert the value to node
        p[i].pro = x[i]
        total = total + p[i].pro
 
        # checking max probability
        if (total > 1) :
            print("Invalid. Enter new values")
            total = total - p[i].pro
            i-=1
         
     
    i+=1
    p[i].pro = 1 - total
    # Sorting the symbols based on
    # their probability or frequency
    sortByProbability(n, p)
 
    for i in range(n):
        p[i].top = -1
 
    # Find the shannon code
    shannon(0, n - 1, p)
 
    # Display the codes
    display(n, p)

Popularity 2/10 Helpfulness 1/10 Language python

Source: www.geeksforgeeks.org

Tags: algorithm python

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Contributed on Sep 18 2023

Jealous Jellyfish

0 Answers Avg Quality 2/10

Python3 program for Shannon Fano Algorithm

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