我正在寻找以下脚本的性能改进。我很确定它可以进行实质性的修改,因为它是我想到的第一件事,所以我做了它,这只是出于我要寻找的演示目的。
I am looking on performance improvement of the script below. I am pretty sure it can be substantially modified, I did it as it was first thing that came to my head and it is only for demonstration purposes on what I am looking for.
function pad(nn, width, z) { z = z || '0'; nn = nn + ''; return nn.length >= width ? nn : new Array(width - nn.length + 1).join(z) + nn; } var makeIntoBinary = function(ii, length) { return pad(ii.toString(2), length); } var makeIntoTrueFalse = function(binary) { var str = ''; for (iii = 0; iii < binary.length; iii++) { if (binary[iii] == '0') { str += ' false'; } else { str += ' true'; } }; console.log(str + ' ' + binary); } var runner = function(n) { var iter = Math.pow(2, n); for (i = 0; i < iter; i++) { makeIntoTrueFalse(makeIntoBinary(i, n)); } }我要寻找的是生成单词集对于所有可能的组合,这些组合实际上是在执行上述二进制操作。 ( runner(2); 会产生 false false , false true , true假, true真),我正在寻找可以让我到达这一点的快速闪电算法。 / p>
What I am looking for is to generate sets of words for all possible combinations which is essentially doing the binary above. (runner(2); would produce false false, false true, true false, true true) I am looking for lightning fast algorithm that gets me to this point.
推荐答案尝试直接操作位,而不进行多余的字符串转换。
Try manipulating bits directly, without extraneous string conversions.
function combinations(n) { var r = []; for(var i = 0; i < (1 << n); i++) { var c = []; for(var j = 0; j < n; j++) { c.push(i & (1 << j) ? 'true' : 'false'); } r.push(c.join(' ')); } return r; } r = combinations(prompt('size?')); document.write(JSON.stringify(r));
就记录而言,这可能会比较慢,但方法更好:
Number.prototype.times = function(fn) { var r = []; for(var i = 0; i < this; i++) r.push(fn(i)); return r; } function combinations(n) { return (1 << n).times(function(i) { return n.times(function(j) { return Boolean(i & 1 << j); }); }); }更多推荐
生成所有可能的单词(“ true”,“ false”)二进制组合
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