正则表达式匹配项缺少一项？ [英] Regex matches missing one match?

问题描述

我有正则表达式 1（0 *）1 和测试字符串 1000010001

I have the regex 1(0*)1 and the test string 1000010001

我想进行2场比赛，但发现只有1场比赛：

I want to have 2 matches, but I find that only 1 gets found :

var regex = new Regex("1(0*)1");
var values = regex.Matches(intBinaryString);
// values only has 1 match

regexonline似乎同意： https://regex101.com/r/3J9Qxj/1

regexonline seems to agree : https://regex101.com/r/3J9Qxj/1

我在做什么错？

推荐答案

您已经在第一个匹配项中选择了第二个零前面的1

You are already selecting the 1 in front of the second zero by the first match.

100001 0001
^^^^^^

这是第一场比赛。其余的只是 0001 ，与您的正则表达式不匹配。

This is the first match. The rest is just 0001 which does not match your regex.

如果您使用先行/后退，则可以避免这种行为：

You can circumvent this behavior if you are using lookaheads/lookbehinds:

(?<=1)(0*)(?=1)

实时示例

因为您无法在JavaScript中使用lookbehinds，足以仅使用一次前瞻来防止重叠：

Because you cannot use lookbehinds in JavaScript, it is enough to only use one lookahead, to prevent the overlapping:

1(0*)(?=1)

实时示例

并提示您 regex101 示例：您没有添加全局标志，这可以防止一种选择。

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