命令来垫零到二进制数的具体位置？

问题描述

我要垫零到二进制数的特定位置。循环二进制数阵列的形式，如 DEC2BIN（43）并添加零和调整大小的声音的车轮的再造。

如何填充零有效地二进制数在Matlab？

循环

 位置= [1,3,6];
X = de2bi（43）;
XX =翻转（X）;KK = 1;
第II = 1：长度（X）+长度（位置）
    如果ISEQUAL（职位（KK），XX（二））
         ％通过一个索引转乘II尾进取，
         因为我觉得我的方法不好％留下来了！
         X（II）= 0;
         位置=位置+ 1;一个现在由于一个填补％持仓量增加
         KK = KK + 1;
    结束
结束
 

这感觉太重塑：基本上如何做到Ÿ像xxxxYabcd到xxxx0Yabcd哪里xxxxYabcd是一个二进制数字前得到0

示例

Output

解决方案

Race begins! Mendo wins, gevang is a good second, thewaywewalk is the third and jaheruddin comes in fourth. The Shai's bitshifting is implemented in the shai function, unfortunately not yet getting it run faster.

Results

gevang :2.2e-05
thewaywewalk :5.6975e-05
mendo :2.2102e-05
jaheruddin :0.0001693
shai (poor hhh-implementation) 5.3288e-04

Warmed-up testing of the answers

function test_padding_zeros()

    function myOutput=gevang(xx,positions)
        nPads = length(positions);
        nPadsShifts = 1:nPads;
        myOutput = ones(1, length(xx) + nPads); % re-indexing on the new array
        myOutput(positions + nPadsShifts) = 0;  % padding values
        myOutput(myOutput==1) = xx;                    % set original bit values
    end

    function myOutput=thewaywewalk(x,positions)
        idx = numel(x):-1:1;
        myOutput = num2cell(x);
        myOutput(2,idx(positions)) = {0};
        myOutput = [myOutput{:}];
    end

    function myOutput=jaheruddin(myInput,positions) % myInput can be a row vector or a matrix!
        n = size(myInput,2)+numel(positions);
        myOutput = false(size(myInput,1),n);
        myOutput(:,setxor((1:length(positions)),1:n))=myInput;
    end

    function myOutput=mendo(myInput,positions)
        myOutput = ones(1,length(myInput)+length(positions));
        myOutput(positions+(1:length(positions))) = 0;
        myOutput(myOutput==1) = myInput;
    end

    function out = bizarreBitShift( bNum, fromBit, shiftAmount )
        % construct a mask
        msk = uint32( (2^( fromBit - 1 ) )-1 ); 
        shiftPart = bitand( uint32(bNum), bitcmp(msk) ); % bitcmp - complement of bits
        staticPart = bitand( uint32(bNum), msk );
        out = bitshift( shiftPart , shiftAmount );
        out = bitor( out, staticPart );
    end

    function myOutput=shai(myInput,positions)
        shiftAmount=1;
        myOutput=sprintf('%d',myInput);
        myOutput=bin2dec(myOutput);
        k=0;
        for ii=1:length(positions)
            fromBit=positions(ii)+k;
            myOutput=bizarreBitShift(myOutput, fromBit, shiftAmount);
            k=k+1;
        end

        myOutput=ismember(dec2bin(myOutput),'1');
    end




positions = [1 3 6]; %// example data
myInput = [1 0 1 0 1 1]; %// example data

ggevang=@() gevang(myInput,positions);
tthewaywewalk=@() thewaywewalk(myInput,positions);
mmendo=@() mendo(myInput,positions);
jjaheruddin=@() jaheruddin(myInput,positions);
sshai=@() shai(myInput,positions);

timeit(ggevang)
timeit(tthewaywewalk)
timeit(mmendo)
timeit(jjaheruddin)
timeit(sshai)

end

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