#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Top 3 Packing Algorithms Implementation

// 1. First Fit Decreasing (FFD) - Bin Packing Algorithm
int compare_desc(const void *a, const void *b) {
    return (*(int*)b - *(int*)a);
}

int firstFit(int bins[], int n, int c) {
    int res = 0;
    
    for (int i = 0; i < n; i++) {
        int j;
        for (j = 0; j < res; j++) {
            if (bins[j] >= bins[i]) {
                bins[j] -= bins[i];
                break;
            }
        }
        
        if (j == res) {
            bins[res] = c - bins[i];
            res++;
        }
    }
    return res;
}

void firstFitDecreasing(int items[], int n, int capacity) {
    // Sort items in decreasing order
    qsort(items, n, sizeof(int), compare_desc);
    
    printf("First Fit Decreasing Algorithm:\n");
    printf("Number of bins required: %d\n", firstFit(items, n, capacity));
}

// 2. Huffman Coding - Compression Algorithm
struct MinHeapNode {
    char data;
    unsigned freq;
    struct MinHeapNode *left, *right;
};

struct MinHeap {
    unsigned size;
    unsigned capacity;
    struct MinHeapNode** array;
};

struct MinHeapNode* newNode(char data, unsigned freq) {
    struct MinHeapNode* temp = (struct MinHeapNode*)malloc(sizeof(struct MinHeapNode));
    temp->left = temp->right = NULL;
    temp->data = data;
    temp->freq = freq;
    return temp;
}

struct MinHeap* createMinHeap(unsigned capacity) {
    struct MinHeap* minHeap = (struct MinHeap*)malloc(sizeof(struct MinHeap));
    minHeap->size = 0;
    minHeap->capacity = capacity;
    minHeap->array = (struct MinHeapNode**)malloc(minHeap->capacity * sizeof(struct MinHeapNode*));
    return minHeap;
}

void swapMinHeapNode(struct MinHeapNode** a, struct MinHeapNode** b) {
    struct MinHeapNode* t = *a;
    *a = *b;
    *b = t;
}

void minHeapify(struct MinHeap* 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) {
        swapMinHeapNode(&minHeap->array[smallest], &minHeap->array[idx]);
        minHeapify(minHeap, smallest);
    }
}

int isSizeOne(struct MinHeap* minHeap) {
    return (minHeap->size == 1);
}

struct MinHeapNode* extractMin(struct MinHeap* minHeap) {
    struct MinHeapNode* temp = minHeap->array[0];
    minHeap->array[0] = minHeap->array[minHeap->size - 1];
    --minHeap->size;
    minHeapify(minHeap, 0);
    return temp;
}

void insertMinHeap(struct MinHeap* minHeap, struct MinHeapNode* 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;
}

void buildMinHeap(struct MinHeap* minHeap) {
    int n = minHeap->size - 1;
    for (int i = (n - 1) / 2; i >= 0; --i)
        minHeapify(minHeap, i);
}

int isLeaf(struct MinHeapNode* root) {
    return !(root->left) && !(root->right);
}

struct MinHeap* createAndBuildMinHeap(char data[], int freq[], int size) {
    struct MinHeap* minHeap = createMinHeap(size);
    for (int i = 0; i < size; ++i)
        minHeap->array[i] = newNode(data[i], freq[i]);
    minHeap->size = size;
    buildMinHeap(minHeap);
    return minHeap;
}

struct MinHeapNode* buildHuffmanTree(char data[], int freq[], int size) {
    struct MinHeapNode *left, *right, *top;
    struct MinHeap* minHeap = createAndBuildMinHeap(data, freq, size);

    while (!isSizeOne(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 printArr(int arr[], int n) {
    printf("Huffman Codes:\n");
    for (int i = 0; i < n; ++i)
        printf("%d ", arr[i]);
    printf("\n");
}

void printCodes(struct MinHeapNode* root, int arr[], int top) {
    if (root->left) {
        arr[top] = 0;
        printCodes(root->left, arr, top + 1);
    }
    if (root->right) {
        arr[top] = 1;
        printCodes(root->right, arr, top + 1);
    }
    if (isLeaf(root)) {
        printf("%c: ", root->data);
        printArr(arr, top);
    }
}

void HuffmanCodes(char data[], int freq[], int size) {
    struct MinHeapNode* root = buildHuffmanTree(data, freq, size);
    int arr[100], top = 0;
    printCodes(root, arr, top);
}

// 3. Run-Length Encoding - Simple Compression Algorithm
void runLengthEncoding(char input[]) {
    int len = strlen(input);
    printf("Run-Length Encoding:\n");
    
    for (int i = 0; i < len; i++) {
        int count = 1;
        while (i < len - 1 && input[i] == input[i+1]) {
            count++;
            i++;
        }
        printf("%c%d", input[i], count);
    }
    printf("\n");
}

int main() {
    printf("Top 3 Packing Algorithms Implementation\n\n");
    
    // Example for First Fit Decreasing
    int items[] = {10, 60, 20, 30, 70, 40, 50};
    int n = sizeof(items)/sizeof(items[0]);
    int capacity = 100;
    firstFitDecreasing(items, n, capacity);
    printf("\n");
    
    // Example for Huffman Coding
    char arr[] = {'A', 'B', 'C', 'D'};
    int freq[] = {5, 9, 12, 13};
    int size = sizeof(arr)/sizeof(arr[0]);
    HuffmanCodes(arr, freq, size);
    printf("\n");
    
    // Example for Run-Length Encoding
    char str[] = "aaabbccccdddd";
    runLengthEncoding(str);
    
    return 0;
}