find & substr

根据分隔符选择需要的子串

#include <iostream>
#include <string>
using namespace std;
int main()
{
    string findee = "This-is-a-string";
    string finder = "This";
    string::size_type n1, n2, n3;
    if ((n1 = findee.find(finder, 0)) != string::npos)
    {
        n2 = findee.find("-", n1);
        n3 = findee.find("-", n2 + 1);
        string sub1, sub2;
        sub1 = findee.substr(n1, n2 - n1);
        sub2 = findee.substr(n2 + 1, n3 - 1 - n2);
        cout << n1 << "," << n2 << "," << n3 << endl;
        cout << findee << endl;
        cout << sub1 << endl;
        cout << sub2 << endl;
    }
    else
        cout << "No found.\n";
}
// 输出
0,4,7
This-is-a-string
This
is

模糊查询

查询所有的“小二”

#include <iostream>
#include <string>
using namespace std;
int main()
{
    string findee = "-王小二-88-张小二-90-";
    string finder = "小二";
    string::size_type n1, n2, n3, last_pos = 0;
    cout << "finder: " << finder << endl;
    while (true)
    {
        string::size_type pos = findee.find(finder, last_pos);
        if (pos != string::npos)
        {
            n1 = findee.rfind("-", pos); // 找到名字前面的 "-"
            n2 = findee.find("-", pos);
            string name = findee.substr(n1 + 1, n2 - n1 - 1);
            cout << name << endl;
            last_pos = n2;
        }
        else
            break;
    }
    return 0;
}
// 输出
finder: 小二
王小二
张小二

字符串倒序

注意，字符串string的 [] 运算符是只读的，不可写，所以需要建立一个字符串 temp 进行赋值

#include <iostream>
#include <string>
using namespace std;
void reverse(string &str)
{
    int i, len = str.size();
    string temp = str;
    for (i = 0; i < len; ++i)
    {
        temp[i] = str[len - 1 - i];
    }
    str = temp;
}
int main()
{
    string str = "你是谁";
    reverse(str);
    cout << str << endl;
    return 0;
}

字符串偏移（加密）

#include <iostream>
#include <string>
using namespace std;
#include <iostream>
#include <string>
using namespace std;
void encode(string &str)
{
    int i, len = str.size();
    string temp = str;
    for (i = 0; i < len; ++i)
    {
        temp[i] = str[len - 1 - i];
    }
    str = temp;
}
void decode(string &str)
{
    int i, len = str.size();
    string temp = str;
    for (i = 0; i < len; ++i)
    {
        temp[i] = str[len - 1 - i] - 15;
    }
    str = temp;
}
int main()
{
    string str = "asddsa";
    encode(str);
    decode(str);
    cout << str << endl;
    return 0;
}
// 输出