#include <stdio.h>
#define MAXBIT 100
#define MAXVALUE 10000          //
#define MAXLEAF 30              //叶节点数目
#define MAXNODE MAXLEAF * 2 - 1 //节点数目
//首先构造出一颗哈夫曼树的结点，包括
//权重weight，父亲parent， 左儿子lchild，右儿子rchild。
typedef struct
{
    int bit[MAXBIT];
    int start;
} HCodeType; //编码结构体
typedef struct HNodeType {
    int weight;
    int parent;
    int lchild;
    int rchild;
} HNodeType; //结点结构体
//开始创建一颗哈夫曼树
void Huffman(HNodeType HuffNode[MAXNODE], int n) {
    int i, j, m1, m2, x1, x2; // i,j循环变量，m1,m2:构造哈弗曼树不同过程中两个最小权值结点的权值
    // x1,x2 构造哈弗曼树不同过程中两个最小权值结点在数组中的序号
    for (i = 0; i < 2 * n - 1; i++) //初始化哈弗曼树数组中的结点
    {
        HuffNode[i].weight = 0;
        HuffNode[i].parent = -1;
        HuffNode[i].lchild = -1;
        HuffNode[i].rchild = -1;
    }
    //输入n个叶子结点的权值
    for (i = 0; i < n; i++) {
        printf("Plese input weight of leaf node %d:\n", i);
        scanf("%d", &HuffNode[i].weight);
    }
    //循环构造哈弗曼树
    for (i = 0; i < n - 1; i++) {
        m1 = m2 = MAXVALUE; // m1,m2中存放两个无父结点且结点权值最小的两个结点
        x1 = x2 = 0;
        //找出所有结点中权值最小、无父节点的两个结点,并合并为一颗二叉树
        for (j = 0; j < n + i; j++) {
            if (HuffNode[j].weight < m1 && HuffNode[j].parent == -1) {
                m2 = m1;
                x2 = x1;
                m1 = HuffNode[j].weight;
                x1 = j;
            } else if (HuffNode[j].weight < m2 && HuffNode[j].parent == -1) {
                m2 = HuffNode[j].weight;
                x2 = j;
            }
        }
        HuffNode[x1].parent = n + i;
        HuffNode[x2].parent = n + i;
        HuffNode[n + i].weight = HuffNode[x2].weight + HuffNode[x1].weight;
        HuffNode[n + i].lchild = x1;
        HuffNode[n + i].rchild = x2;
    }
}
/*
5
10 15 30 16 29
*/
int main() {
    HNodeType HuffNode[MAXNODE];     //定义一个结点结构体数组
    HCodeType HuffCode[MAXLEAF], cd; //定义一个编码结构体数组，同时定义一个临时变量来存放求解编码时的信息
    int i, j, c, n, p;
    printf("Please input n:\n");
    scanf("%d", &n);
    Huffman(HuffNode, n);

    for (i = 0; i < n; i++) {
        cd.start = n - 1;
        c = i;
        p = HuffNode[c].parent;
        while (p != -1) //父节点存在
        {
            if (HuffNode[p].lchild == c) {
                cd.bit[cd.start] = 0;
            } else {
                cd.bit[cd.start] = 1;
            }
            cd.start--; //求编码的低一位
            c = p;
            p = HuffNode[c].parent; //设置下一循环条件
        }
        for (j = cd.start + 1; j < n; j++) {
            HuffCode[i].bit[j] = cd.bit[j];
        }
        HuffCode[i].start = cd.start;
    }
    for (i = 0; i < n; i++) {
        printf("%d 's Huffman code is:", i);
        for (j = HuffCode[i].start + 1; j < n; j++) {
            printf("%d", HuffCode[i].bit[j]);
        }
        printf("\n");
    }
    getchar();
    return 0;
}