代码之家 › 专栏 › 技术社区 › user8098743

合并/优化子字符串语句

indexof stringbuilder substring optimization c#

user8098743 · 技术社区 · 7 年前

string page = wc.DownloadString("https://www.youtube.com/browse_ajax?action_continuation=1&continuation=4qmFsgI8EhhVQ2ZXdHFQeUJNR183aTMzT2VlTnNaWncaIEVnWjJhV1JsYjNNZ0FEQUJPQUZnQVdvQWVnRTB1QUVB");
int pos;
while ((pos = page.IndexOf("/watch?v=")) > 0) {
    page = page.Substring(pos);
    page = page.Substring(page.IndexOf("video-time"));
    page = page.Substring(page.IndexOf("aria-label"));
    page = page.Substring(page.IndexOf(@"\u003e") + 6);
    string vt = page.Substring(0, page.IndexOf(@"\u003c"));
    page = page.Substring(page.IndexOf("title=") + 1);
    page = page.Substring(page.IndexOf("title=") + 1);
    page = page.Substring(page.IndexOf("title=") + 1);
    page = page.Substring(page.IndexOf("\\\"") + 2);
    string tt = page.Substring(0, page.IndexOf("\\\"  aria-describedby="));
}

可悲的是,我不能跳过一些 Substring vt 和 tt 自从 子字符串 总是返回我尝试解决方案的新字符串 StringBuilder :

System.Text.StringBuilder sb=new System.Text.StringBuilder(wc.DownloadString("https://www.youtube.com/browse_ajax?action_continuation=1&continuation=4qmFsgI8EhhVQ2ZXdHFQeUJNR183aTMzT2VlTnNaWncaIEVnWjJhV1JsYjNNZ0FEQUJPQUZnQVdvQWVnRTB1QUVB"));
int pos;
while ((pos = sb.ToString().IndexOf("/watch?v=")) > 0) {
    sb.Remove(0,pos);
    sb.Remove(0,sb.ToString().IndexOf("video-time"));
    sb.Remove(0,sb.ToString().IndexOf("aria-label"));
    sb.Remove(0,sb.ToString().IndexOf(@"\u003e") + 6);
    string vt =sb.ToString(0,sb.ToString().IndexOf(@"\u003c"));
    sb.Remove(0,sb.ToString().IndexOf("title=") + 1);
    sb.Remove(0,sb.ToString().IndexOf("title=") + 1);
    sb.Remove(0,sb.ToString().IndexOf("title=") + 1);
    sb.Remove(0,sb.ToString().IndexOf("\\\"") + 2);
    string tt =sb.ToString(0,sb.ToString().IndexOf("\\\"  aria-describedby="));
}

ToString() ,确实稍微快一点。

现在,有没有办法进一步优化这一点?甚至可以让它看起来更好?

2 回复 | 直到 7 年前

user8098743 user8098743 7 年前

根据@harold的建议

string page = wc.DownloadString("https://www.youtube.com/browse_ajax?action_continuation=1&continuation=4qmFsgI8EhhVQ2ZXdHFQeUJNR183aTMzT2VlTnNaWncaIEVnWjJhV1JsYjNNZ0FEQUJPQUZnQVdvQWVnRTB1QUVB");
int pos;
while ((pos = page.IndexOf("/watch?v=")) > 0) {
    int subPos=pos;
    subPos=page.IndexOf("video-time",subPos);
    subPos=page.IndexOf("aria-label",subPos);
    subPos=page.IndexOf(@"\u003e",subPos);
    subPos+=6;
    string vt=page.Substring(subPos,(subPos=page.IndexOf(@"\u003c",subPos)));
    subPos=page.IndexOf("title=",subPos);
    subPos++;
    subPos=page.IndexOf("title=",subPos);
    subPos++;
    subPos=page.IndexOf("title=",subPos);
    subPos=page.IndexOf("\\\"",subPos);
    subPos+=2;
    string tt=page.Substring(subPos,(subPos=page.IndexOf("\\\"  aria-describedby=", subPos)));
    page=page.Substring(subPos);
}

似乎比使用 StringBuilder 具有 ToString()

user8098743 user8098743 7 年前

these extension methods

System.Text.StringBuilder sb=new System.Text.StringBuilder(wc.DownloadString("https://www.youtube.com/browse_ajax?action_continuation=1&continuation=4qmFsgI8EhhVQ2ZXdHFQeUJNR183aTMzT2VlTnNaWncaIEVnWjJhV1JsYjNNZ0FEQUJPQUZnQVdvQWVnRTB1QUVB"));
int pos;
while ((pos = sb.ToString().IndexOf("/watch?v=")) > 0) {
    sb.Remove(0,pos);
    sb.Remove(0,sb.IndexOf("video-time"));
    sb.Remove(0,sb.IndexOf("aria-label"));
    sb.Remove(0,sb.IndexOf(@"\u003e") + 6);
    string vt =sb.ToString(0,sb.IndexOf(@"\u003c"));
    sb.Remove(0,sb.IndexOf("title=") + 1);
    sb.Remove(0,sb.IndexOf("title=") + 1);
    sb.Remove(0,sb.IndexOf("title=") + 1);
    sb.Remove(0,sb.IndexOf("\\\"") + 2);
    string tt =sb.ToString(0,sb.IndexOf("\\\"  aria-describedby="));
}

应该比使用更快 StringBuilder ToString() ,我的测试结果有点不稳定。