C :

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
#define OVERFLOW -1
#define MAX_TREE_SIZE 100
typedef int Status;
typedef struct {
        unsigned int weight;
        unsigned int parent,lchild,rchild;
}HTNode,*HuffmanTree; 
typedef char **HuffmanCode; 
int min1(HuffmanTree t,int i) { 
        int j,flag;
        unsigned int k=UINT_MAX; 
        for(j=1;j<=i;j++)
                if(t[j].weight<k&&t[j].parent==0)
                        k=t[j].weight,flag=j;
        t[flag].parent=1;
        return flag;
}

void select(HuffmanTree t,int i,int *s1,int *s2) {
        int j;
        *s1=min1(t,i);
        *s2=min1(t,i);
        if(*s1>*s2) {
                j=*s1;
                *s1=*s2;
                *s2=j;
        }
}

void HuffmanCoding(HuffmanTree *HT,HuffmanCode *HC,int *w,int n) { 
        int m,i,s1,s2,start;
        unsigned c,f;
        HuffmanTree p;
        char *cd;
        if(n<=1) return;
        m=2*n-1;
        *HT=(HuffmanTree)malloc((m+1)*sizeof(HTNode));
        for(p=*HT+1,i=1;i<=n;++i,++p,++w) {
                (*p).weight=*w; (*p).parent=(*p).lchild=(*p).rchild=0;
        }
        for(;i<=m;++i,++p) (*p).parent=0;
        for(i=n+1;i<=m;++i) { 
                select(*HT,i-1,&s1,&s2);
                (*HT)[s1].parent=(*HT)[s2].parent=i;
                (*HT)[i].lchild=s1;
                (*HT)[i].rchild=s2;
                (*HT)[i].weight=(*HT)[s1].weight+(*HT)[s2].weight;
        }
        *HC=(HuffmanCode)malloc((n+1)*sizeof(char*));
        cd=(char*)malloc(n*sizeof(char)); 
        cd[n-1]='\0'; 
        for(i=1;i<=n;i++) {
                start=n-1;
                for(c=i,f=(*HT)[i].parent;f!=0;c=f,f=(*HT)[f].parent)
                if((*HT)[f].lchild==c) cd[--start]='0';
                else cd[--start]='1';
                (*HC)[i]=(char*)malloc((n-start)*sizeof(char));
                strcpy((*HC)[i],&cd[start]);
        }
        free(cd); 
}

int main() {
        HuffmanTree HT;
        HuffmanCode HC;
        int *w,n,i,c;
        scanf("%d",&n);
        c=n;
        w=(int*)malloc(n*sizeof(int));
        for(i=0;i<=n-1;i++)
                scanf("%d",w+i);
        HuffmanCoding(&HT,&HC,w,n);
        while(n--) puts(HC[c-n]);
        return 0;
}

C++ :

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
#define OVERFLOW -1
#define MAX_TREE_SIZE 100
typedef int Status; /* 函数结果状态代码,如OK等 */
typedef struct {
	unsigned int weight;
	unsigned int parent,lchild,rchild;
}HTNode,*HuffmanTree; /* 动态分配数组存储赫夫曼树 */
typedef char **HuffmanCode; /* 动态分配数组存储赫夫曼编码表 */

int min1(HuffmanTree t,int i) { /* 函数void select()调用 */
	int j,flag;
	unsigned int k=UINT_MAX; /* 取k为不小于可能的值 */
	for(j=1;j<=i;j++)
		if(t[j].weight<k&&t[j].parent==0)
			k=t[j].weight,flag=j;
	t[flag].parent=1;
	return flag;
}

void select(HuffmanTree t,int i,int *s1,int *s2) {
/* s1为最小的两个值中序号小的那个 */
	int j;
	*s1=min1(t,i);
	*s2=min1(t,i);
	if(*s1>*s2) {
		j=*s1;
		*s1=*s2;
		*s2=j;
	}
}

void HuffmanCoding(HuffmanTree *HT,HuffmanCode *HC,int *w,int n) { /* 算法6.12 */
/* w存放n个字符的权值(均>0),构造赫夫曼树HT,并求出n个字符的赫夫曼编码HC */
	int m,i,s1,s2,start;
	unsigned c,cdlen;
	HuffmanTree p;
	char *cd;
	if(n<=1) return;
	m=2*n-1;
	*HT=(HuffmanTree)malloc((m+1)*sizeof(HTNode)); /* 0号单元未用 */
	for(p=*HT+1,i=1;i<=n;++i,++p,++w) {
		(*p).weight=*w; (*p).parent=(*p).lchild=(*p).rchild=0;
	}
	for(;i<=m;++i,++p) (*p).parent=0;
	for(i=n+1;i<=m;++i) { /* 建赫夫曼树 */
	/* 在HT[1~i-1]中选择parent为0且weight最小的两个结点,其序号分别为s1和s2 */
		select(*HT,i-1,&s1,&s2);
		(*HT)[s1].parent=(*HT)[s2].parent=i;
		(*HT)[i].lchild=s1;
		(*HT)[i].rchild=s2;
		(*HT)[i].weight=(*HT)[s1].weight+(*HT)[s2].weight;
	}
	/* 以下为算法6.13，无栈非递归遍历赫夫曼树,求赫夫曼编码，以上同算法6.12 */
	*HC=(HuffmanCode)malloc((n+1)*sizeof(char*));
	/* 分配n个字符编码的头指针向量([0]不用) */
	cd=(char*)malloc(n*sizeof(char)); /* 分配求编码的工作空间 */
	c=m;
	cdlen=0;
	for(i=1;i<=m;++i)
	(*HT)[i].weight=0; /* 遍历赫夫曼树时用作结点状态标志 */
	while(c) {
		if((*HT)[c].weight==0) { /* 向左 */
			(*HT)[c].weight=1;
			if((*HT)[c].lchild!=0) {
				c=(*HT)[c].lchild;
				cd[cdlen++]='0';
			} else if((*HT)[c].rchild==0) { /* 登记叶子结点的字符的编码 */
				(*HC)[c]=(char *)malloc((cdlen+1)*sizeof(char));
				cd[cdlen]='\0';
				strcpy((*HC)[c],cd); /* 复制编码(串) */
			}
		} else if((*HT)[c].weight==1) { /* 向右 */
			(*HT)[c].weight=2;
			if((*HT)[c].rchild!=0) {
				c=(*HT)[c].rchild;
				cd[cdlen++]='1';
			}
		} else { /* HT[c].weight==2,退回 */
			(*HT)[c].weight=0;
			c=(*HT)[c].parent;
			--cdlen; /* 退到父结点,编码长度减1 */
		}
	}
	free(cd);
}

int main() {
	HuffmanTree HT;
	HuffmanCode HC;
	int *w,n,i;
	scanf("%d",&n);
	w=(int*)malloc(n*sizeof(int));
	for(i=0;i<=n-1;i++)
		scanf("%d",w+i);
	HuffmanCoding(&HT,&HC,w,n);
	for(i=1;i<=n;i++) puts(HC[i]);
}