function   X=lsjfft(x);%x為輸入的序列
M=nextpow2(length(x));%求大于等于x長度的2的最小次冪
N=pow2(M);
if length(x)<N;
    x=[x,zeros(1,N-length(x))];%若x的長度小于N,補N-length(x)個0
          end
rev_order=bin2dec(fliplr(dec2bin([1:N]-1,M)))+1;%求數列1:N的倒序,dec2bin()十進制轉換為二進制,
                                                ;%bin2dec()二進制轉換為十進制,fliplr()
X=x(rev_order);  % 將x倒序后作為輸入X
for L=1:M
    B=2^(L-1);
    W=exp(-j*2*pi/N);
    for J=1:B
        p=2^(M-L)*(J-1);
        for K=J:2^L:N
            W=W^p;
            X(K)=X(K)+X(K+B)*W;
            X(K+B)=X(K)-X(K+B)*W;
        end
    end
end