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如何优化stringrfind函数在SEO中更高效

一、简介

stringrfind函数是C++ STL库中的一个函数,通常用于寻找某个字符串在给定字符串中最后一次出现的位置。在搜索引擎优化(SEO)中,这个函数的效率对于网页的加载速度和搜索结果排名都有着重要的影响。因此,如何优化这个函数是程序员们需要重点关注的问题之一。

二、优化方案

1.字符串预处理

字符串预处理是一种常见的优化方案,其目的是将需要查找的字符串进行预处理,以提高查找速度。比如,可以将待查找的字符串中的大小写字母全部转化为小写字母或大写字母,这样可以减少查找时需要比对的字符集合,从而提高查找速度。

std::string toLowerCase(std::string str){
    for(int i = 0; i < str.length(); i++){
        if(str[i] >= 'A' && str[i] <= 'Z'){
            str[i] += 32;
        }
    }
    return str;
}
int stringrfind(std::string str, std::string substr){
    str = toLowerCase(str);
    substr = toLowerCase(substr);
    return str.rfind(substr);
}

2.使用KMP算法

KMP算法是一种字符串匹配算法,其时间复杂度为O(N+M),比一般的暴力匹配算法要快很多。可以将待查找的字符串和要匹配的字符串都进行KMP算法处理,以提高查找速度。但是需要注意的是,这个方法在处理较短的字符串时,可能会造成额外的开销。

std::vector computeLPS(std::string substr){
    int n = substr.length();
    std::vector
    lps(n);
    int len = 0;
    lps[0] = 0;
    for(int i = 1; i < n; ){
        if(substr[i] == substr[len]){
            len++;
            lps[i] = len;
            i++;
        }
        else{
            if(len != 0){
                len = lps[len-1];
            }
            else{
                lps[i] = 0;
                i++;
            }
        }
    }
    return lps;
}
int stringrfind(std::string str, std::string substr){
    std::vector
     lps = computeLPS(substr);
    int n = str.length();
    int m = substr.length();
    int i = 0, j = 0, pos = -1;
    while(i < n){
        if(str[i] == substr[j]) {
            i++;
            j++;
        }
        if(j == m){
            pos = i - j;
            j = lps[j-1];
        }
        else if(i < n && str[i] != substr[j]){
            if(j != 0){
                j = lps[j-1];
            }
            else{
                i++;
            }
        }
    }
    return pos;
}

    
   
  

3.使用Boyer-Moore算法

Boyer-Moore算法是一种字符串匹配算法,其时间复杂度为O(N)。这个算法的效率非常高,因为它采用的是一种贪心策略,可以跨越多个字符进行匹配。和KMP一样,可以将待查找的字符串和要匹配的字符串都进行Boyer-Moore算法处理,以提高查找速度。

int stringrfind(std::string str, std::string substr){
    int n = str.length();
    int m = substr.length();
    std::vector last(256, -1);
    for(int i = 0; i < m; i++){
        last[int(substr[i])] = i;
    }
    int i = m-1, j = m-1;
    while(i < n && j >= 0){
        if(str[i] == substr[j]){
            i--;
            j--;
        }
        else{
            i += m - std::min(j, 1 + last[int(str[i])]);
            j = m - 1;
        }
    }
    if(j == -1){
        return i+1;
    }
    else{
        return -1;
    }
}

  

三、总结

本文介绍了优化stringrfind函数的三种方法,包括字符串预处理、KMP算法和Boyer-Moore算法。程序员可以根据自身的需求和实际情况选择所需的方法,以提高程序的运行效率和程序在SEO方面的表现。

如何优化stringrfind函数在SEO中更高效

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when-present<#else>when-missing. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)?? ---- ---- FTL stack trace ("~" means nesting-related): - Failed at: ${item.id} [in template "article/detail/index.ftl" at line 48, column 106] ---- Java stack trace (for programmers): ---- freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...] at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134) at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481) at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401) at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370) at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:104) at freemarker.core.DollarVariable.accept(DollarVariable.java:63) at freemarker.core.Environment.visit(Environment.java:371) at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321) at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271) at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244) at freemarker.core.Environment.visitIteratorBlock(Environment.java:645) at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108) at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94) at freemarker.core.Environment.visit(Environment.java:335) at freemarker.core.Environment.visit(Environment.java:341) at freemarker.core.Environment.visit(Environment.java:341) at freemarker.core.Environment.process(Environment.java:314) at freemarker.template.Template.process(Template.java:383) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:332) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:266) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:220) at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:181) at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:314) at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1431) at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1167) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1106) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at com.software.filter.HttpSpiderIdentifyFilter.doFilter(HttpSpiderIdentifyFilter.java:51) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:340) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1744) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) at java.base/java.lang.VirtualThread.run(VirtualThread.java:309)