function [h,s]=huffman(p)

% Huffman 哈夫曼碼生成器，返回哈夫曼碼矩陣h和一個概率向量為p的信源的碼字長度

if length(find(p<0))~=0
    error('Not a Prob. vector, negative component(s)');
end

if abs(sum(p)-1)>10e-10
    error('Not a prob. vector, components do not add up to 1');
end



n=length(p);
q=p;
m=zeros(n-1,n);

for i=1:n-1
    [q,s]=sort(q);          %sort是一個排序函數，q是排序后的向量，s是新向量在原始向量的位置
    m(i,:)=[s(1:n-i+1),zeros(1,i-1)];
    q=[q(1)+q(2),q(3:n),1];  
end

for i=1:n-1
    c(i,:)=blanks(n*n);
%     c
    
end

c(n-1,n)='1';
c(n-1,2*n)='0';

for i=2:n-1
    c(n-i,1:n-1)=c(n-i+1,n*(find(m(n-i+1,:)==1))-(n-2):n*(find(m(n-i+1,:)==1)));
    c(n-i,n)='1';
    c(n-i,n+1:2*n-1)=c(n-i,1:n-1);
    c(n-i,2*n)='0';
    for j=1:i-1
        c(n-i,(j+1)*n+1:(j+2)*n)=c(n-i+1,n*(find(m(n-i+1,:)==j+1)-1)+1:n*find(m(n-i+1,:)==j+1));
    end
end

for i=1:n
    h(i,1:n)=c(1,n*(find(m(1,:)==i)-1)+1:find(m(1,:)==i)*n);
    ss(i)=length(find(abs(h(i,:))~=32));
end

s=sum(p.*ss);