Example 1: huffman coding python
import math
import sys
global probabilities
probabilities = []
class HuffmanCode:
def __init__(self,probability):
self.probability = probability
def position(self, value, index):
for j in range(len(self.probability)):
if(value >= self.probability[j]):
return j
return index-1
def characteristics_huffman_code(self, code):
length_of_code = [len(k) for k in code]
mean_length = sum([a*b for a, b in zip(length_of_code, self.probability)])
print("Average length of the code: %f" % mean_length)
print("Efficiency of the code: %f" % (entropy_of_code/mean_length))
def compute_code(self):
num = len(self.probability)
huffman_code = ['']*num
for i in range(num-2):
val = self.probability[num-i-1] + self.probability[num-i-2]
if(huffman_code[num-i-1] != '' and huffman_code[num-i-2] != ''):
huffman_code[-1] = ['1' + symbol for symbol in huffman_code[-1]]
huffman_code[-2] = ['0' + symbol for symbol in huffman_code[-2]]
elif(huffman_code[num-i-1] != ''):
huffman_code[num-i-2] = '0'
huffman_code[-1] = ['1' + symbol for symbol in huffman_code[-1]]
elif(huffman_code[num-i-2] != ''):
huffman_code[num-i-1] = '1'
huffman_code[-2] = ['0' + symbol for symbol in huffman_code[-2]]
else:
huffman_code[num-i-1] = '1'
huffman_code[num-i-2] = '0'
position = self.position(val, i)
probability = self.probability[0:(len(self.probability) - 2)]
probability.insert(position, val)
if(isinstance(huffman_code[num-i-2], list) and isinstance(huffman_code[num-i-1], list)):
complete_code = huffman_code[num-i-1] + huffman_code[num-i-2]
elif(isinstance(huffman_code[num-i-2], list)):
complete_code = huffman_code[num-i-2] + [huffman_code[num-i-1]]
elif(isinstance(huffman_code[num-i-1], list)):
complete_code = huffman_code[num-i-1] + [huffman_code[num-i-2]]
else:
complete_code = [huffman_code[num-i-2], huffman_code[num-i-1]]
huffman_code = huffman_code[0:(len(huffman_code)-2)]
huffman_code.insert(position, complete_code)
huffman_code[0] = ['0' + symbol for symbol in huffman_code[0]]
huffman_code[1] = ['1' + symbol for symbol in huffman_code[1]]
if(len(huffman_code[1]) == 0):
huffman_code[1] = '1'
count = 0
final_code = ['']*num
for i in range(2):
for j in range(len(huffman_code[i])):
final_code[count] = huffman_code[i][j]
count += 1
final_code = sorted(final_code, key=len)
return final_code
string = input("Enter the string to compute Huffman Code: ")
freq = {}
for c in string:
if c in freq:
freq[c] += 1
else:
freq[c] = 1
freq = sorted(freq.items(), key=lambda x: x[1], reverse=True)
length = len(string)
probabilities = [float("{:.2f}".format(frequency[1]/length)) for frequency in freq]
probabilities = sorted(probabilities, reverse=True)
huffmanClassObject = HuffmanCode(probabilities)
P = probabilities
huffman_code = huffmanClassObject.compute_code()
print(' Char | Huffman code ')
print('----------------------')
for id,char in enumerate(freq):
if huffman_code[id]=='':
print(' %-4r |%12s' % (char[0], 1))
continue
print(' %-4r |%12s' % (char[0], huffman_code[id]))
huffmanClassObject.characteristics_huffman_code(huffman_code)
Example 2: huffman coding algorithm code
// Huffman Coding in C++
using namespace std;
struct MinHNode {
unsigned freq;
char item;
struct MinHNode *left, *right;
};
struct MinH {
unsigned size;
unsigned capacity;
struct MinHNode **array;
};
// Creating Huffman tree node
struct MinHNode *newNode(char item, unsigned freq) {
struct MinHNode *temp = (struct MinHNode *)malloc(sizeof(struct MinHNode));
temp->left = temp->right = NULL;
temp->item = item;
temp->freq = freq;
return temp;
}
// Create min heap using given capacity
struct MinH *createMinH(unsigned capacity) {
struct MinH *minHeap = (struct MinH *)malloc(sizeof(struct MinH));
minHeap->size = 0;
minHeap->capacity = capacity;
minHeap->array = (struct MinHNode **)malloc(minHeap->capacity * sizeof(struct MinHNode *));
return minHeap;
}
// Swap function
void swapMinHNode(struct MinHNode **a, struct MinHNode **b) {
struct MinHNode *t = *a;
*a = *b;
*b = t;
}
// Heapify
void minHeapify(struct MinH *minHeap, int idx) {
int smallest = idx;
int left = 2 * idx + 1;
int right = 2 * idx + 2;
if (left < minHeap->size && minHeap->array[left]->freq < minHeap->array[smallest]->freq)
smallest = left;
if (right < minHeap->size && minHeap->array[right]->freq < minHeap->array[smallest]->freq)
smallest = right;
if (smallest != idx) {
swapMinHNode(&minHeap->array[smallest],
&minHeap->array[idx]);
minHeapify(minHeap, smallest);
}
}
// Check if size if 1
int checkSizeOne(struct MinH *minHeap) {
return (minHeap->size == 1);
}
// Extract the min
struct MinHNode *extractMin(struct MinH *minHeap) {
struct MinHNode *temp = minHeap->array[0];
minHeap->array[0] = minHeap->array[minHeap->size - 1];
--minHeap->size;
minHeapify(minHeap, 0);
return temp;
}
// Insertion
void insertMinHeap(struct MinH *minHeap, struct MinHNode *minHeapNode) {
++minHeap->size;
int i = minHeap->size - 1;
while (i && minHeapNode->freq < minHeap->array[(i - 1) / 2]->freq) {
minHeap->array[i] = minHeap->array[(i - 1) / 2];
i = (i - 1) / 2;
}
minHeap->array[i] = minHeapNode;
}
// BUild min heap
void buildMinHeap(struct MinH *minHeap) {
int n = minHeap->size - 1;
int i;
for (i = (n - 1) / 2; i >= 0; --i)
minHeapify(minHeap, i);
}
int isLeaf(struct MinHNode *root) {
return !(root->left) && !(root->right);
}
struct MinH *createAndBuildMinHeap(char item[], int freq[], int size) {
struct MinH *minHeap = createMinH(size);
for (int i = 0; i < size; ++i)
minHeap->array[i] = newNode(item[i], freq[i]);
minHeap->size = size;
buildMinHeap(minHeap);
return minHeap;
}
struct MinHNode *buildHfTree(char item[], int freq[], int size) {
struct MinHNode *left, *right, *top;
struct MinH *minHeap = createAndBuildMinHeap(item, freq, size);
while (!checkSizeOne(minHeap)) {
left = extractMin(minHeap);
right = extractMin(minHeap);
top = newNode('$', left->freq + right->freq);
top->left = left;
top->right = right;
insertMinHeap(minHeap, top);
}
return extractMin(minHeap);
}
void printHCodes(struct MinHNode *root, int arr[], int top) {
if (root->left) {
arr[top] = 0;
printHCodes(root->left, arr, top + 1);
}
if (root->right) {
arr[top] = 1;
printHCodes(root->right, arr, top + 1);
}
if (isLeaf(root)) {
cout << root->item << " | ";
printArray(arr, top);
}
}
// Wrapper function
void HuffmanCodes(char item[], int freq[], int size) {
struct MinHNode *root = buildHfTree(item, freq, size);
int arr[MAX_TREE_HT], top = 0;
printHCodes(root, arr, top);
}
// Print the array
void printArray(int arr[], int n) {
int i;
for (i = 0; i < n; ++i)
cout << arr[i];
cout << "\n";
}
int main() {
char arr[] = {'A', 'B', 'C', 'D'};
int freq[] = {5, 1, 6, 3};
int size = sizeof(arr) / sizeof(arr[0]);
cout << "Char | Huffman code ";
cout << "\n----------------------\n";
HuffmanCodes(arr, freq, size);
}