C++ string内的搜索

小鱼儿 2022-05-19 22:40 127阅读 0赞

## 用find\_first\_of和find\_first\_not\_of找出string中的数字和字母字符 ##

#include"stdafx.h"
    #include<iostream>
    #include<string>
    //#include "ProgramRunClock.h"
    //#include<vector>
    //#include<list>
    //#include<time.h>
    using namespace std;
    
    int main(int argc, char **argv) {
        string base = "ab2c3d7R4E6";
        string digits, letters;
        size_t index = 0;
        while (true)
        {
            index = base.find_first_of("0123456789", index);
            if (index == base.npos)break;
            digits.push_back(base[index]);
            index++;
        }
        index = 0;
        while (true)
        {
            index = base.find_first_not_of("0123456789", index);
            if (index == base.npos)break;
            letters.push_back(base[index]);
            index++;
        }
        cout << digits << endl << letters << endl;
        return 0;
    }

## 读取字符串(单词)文件筛选出不含特定字母的单词 ##

#include"stdafx.h"
    #include<iostream>
    #include<string>
    #include<fstream>
    //#include "ProgramRunClock.h"
    #include<vector>
    //#include<list>
    //#include<time.h>
    using namespace std;
    
    int main(int argc, char **argv) {
        ifstream wordgetin(argv[1]);
        string temp;
        vector<string> words, eligibleWords; 
        string comparewith{ "bdfgjpqy" };
        while (wordgetin >> temp)words.emplace_back(temp);
        for (auto word : words)
        {
            if (word.find_first_of(comparewith) == word.npos)eligibleWords.emplace_back(word);
        }
        for (auto word : eligibleWords)
        {
            cout << word << endl;
        }
        return 0;
    }

## 在stringvector里计算包含数字的字符串元素转化后的和 ##

#include"stdafx.h"
    #include<iostream>
    #include<string>
    #include<fstream>
    //#include "ProgramRunClock.h"
    #include<vector>
    //#include<list>
    //#include<time.h>
    using namespace std;
    float VecTransformSum(vector<string> svec)
    {
        float sum = 0;
        string buffer;
        for (auto itr = svec.begin(); itr != svec.end(); itr++)
        {
            buffer = *itr;
            buffer = buffer.substr(buffer.find_first_of("+-.0123456789"));
            sum += stof(buffer);
        }
        return sum;
    }
    int main(int argc, char **argv) {
        vector<string> ivec{
       "hda1.2","bdax2.4","scaf3.1","lwefeafewagfes4.6","yafafaq5.6"};
        cout << VecTransformSum(ivec) << endl;
        return 0;
    }

## 一个用string内部函数,将不同类型的日期转化为标准格式的类 ##

#include"stdafx.h"
    #include<iostream>
    #include<string>
    #include<fstream>
    #include<sstream>
    //#include "ProgramRunClock.h"
    #include<vector>
    //#include<list>
    //#include<time.h>
    using namespace std;
    class YearMonthDay
    {
    public:
        YearMonthDay() = default;
        YearMonthDay(const string &base);
        const string getdatestr()
        {
            stringstream buffer;
            string temp, result;
            buffer << year; buffer >> temp; result.append(temp + "年"); buffer.clear();
            buffer << month; buffer >> temp; result.append(temp + "月"); buffer.clear();
            buffer << day; buffer >> temp; result.append(temp+"日");
            return result;
        }
    private:
        unsigned year = 1970;
        unsigned month = 1;
        unsigned day = 1;
    };
    YearMonthDay::YearMonthDay(const string &base)
    {
       //在这些vector里找月数关键词
        string str_year, str_month, str_day;
        bool english_month = false;
        vector<string> uppercase{ "January","February" ,"March", "April", "May" ,"June" ,"July", "August" ,"September" ,"October" ,"November" ,"December"};
        vector<string> lowercase{ "january","february" ,"march", "april", "may" ,"june" ,"july", "august" ,"september" ,"october" ,"november" ,"december" };
        vector<string> uppercase_abbreviation{ "Jan","Feb" ,"Mar", "Apr", "May" ,"Jun" ,"Jul", "Aug" ,"Sep" ,"Oct" ,"Nov" ,"Dec" };
        vector<string> lowercase_abbreviation{ "jan","feb" ,"mar", "apr", "may" ,"jun" ,"jul", "aug" ,"sep" ,"oct" ,"nov" ,"dec" };
        for (size_t index = 0; index != 12; index++)
        {
       //根据下标用find找4个vector中对应的作为base子字符串的元素
            size_t search_one = base.find(uppercase[index]), 
                search_two = base.find(lowercase[index]),
                search_three = base.find(uppercase_abbreviation[index]),
                search_four = base.find(lowercase_abbreviation[index]);//在四个vector里找到的子串的首字符位置
            if (search_one!=base.npos)
            {
                month = index + 1;
                str_month = uppercase[index];
                english_month = true;
                break;
            }
            if (search_two != base.npos)
            {
                month = index + 1;//如果能找到就根据下标给month赋值
                str_month = lowercase[index];
                english_month = true;
                break;
            }
            if (search_three != base.npos)
            {
                month = index + 1;
                str_month = uppercase_abbreviation[index];
                english_month = true;
                break;
            }
            if (search_four != base.npos)
            {
                month = index + 1;
                str_month = lowercase_abbreviation[index];
                english_month = true;
                break;
            }
        }
    
        vector<string> years_compare;
        stringstream buffer;
        string temp;
        for (size_t y = 1900; y <= 2100; y++)
        {
            buffer << y;
            buffer >> temp;
            years_compare.emplace_back(temp);
            buffer.clear();
        }//年份vector一共200年 1900-2100
        for (size_t index = 0; index <= 200; index++)
        {
            size_t search = base.find(years_compare[index]);
            if (search != base.npos)
            {
                year = 1900 + index;
                str_year = years_compare[index];
                break;
            }//比较找一下是哪一年，更新year值
        }
    
        size_t search_year = base.find(str_year);
        if (search_year == base.size() - 4)
        {
            size_t search_day = base.find_first_of("0123456789");
            str_day.push_back(base[search_day]);
            if (isdigit(base[search_day + 1]))str_day.push_back(base[search_day + 1]);
            stringstream buffer;
            buffer << str_day; buffer >> day; buffer.clear();
            if (!english_month)
            {
                size_t month_index = search_day+2;
                while (!isdigit(base[month_index]))month_index++;
                while (isdigit(base[month_index]))
                {
                    str_month.push_back(base[month_index]);
    
                    month_index++;
                }
                buffer << str_month; buffer >> month;
            }
    
        }
        else
        {
            size_t month_index = 5;
            while (isdigit(base[month_index]))
            {
                str_month.push_back(base[month_index]);
                month_index++;
            }
            month_index++;
            while (isdigit(base[month_index]))
            {
                str_day.push_back(base[month_index]);
                month_index++;
            }
            buffer << str_month; buffer >> month; buffer.clear();
            buffer << str_day; buffer >> day;
        }
    }
    int main(int argc, char **argv) {
        const string testfilelocation = argv[1];
    
        ifstream datetestgetlineinput(testfilelocation);
        if (datetestgetlineinput)cout << "创建名为datetestgetlineinput的文件输入流成功,文件位置: " << testfilelocation << endl;
        else cout << "创建名为datetestgetlineinput的文件输入流失败" << endl;
        string datestr;
        while (!datetestgetlineinput.eof())
        {
            cout << "输入要转化为标准格式的日期字符串: ";
            getline(datetestgetlineinput, datestr);
            cout << datestr << endl;
            YearMonthDay date(datestr);
            datestr.clear();
            cout << date.getdatestr() << endl;
        }
        datetestgetlineinput.close();
        return 0;
    }

**不能转化很多类型的日期，只针对这几种**  
![这里写图片描述][70]

**运行结果**  
![这里写图片描述][70 1]

[70]: /images/20220520/31a618bcf4744758a660c623074f4033.png
[70 1]: /images/20220520/ea597ba7897f4f6eb24ae5d4c06c2e0e.png