关于c++:c-获取数字字符串字串

c++ 获取数字字符串的子串数值，比方给定字符串"123456",要获取第三位和第四位的数值，这里是34。

应用substr

应用substr截取字串，再应用c_str()获取字符数组，再应用atoi()转换为数字

结构字符数组

间接应用索引获取字符，构建字符数组，再应用atoi()转换为数字

代码

#include <string>#include <iostream>#include <chrono>using namespace std;int main(int argc, char* argv[]) {    string val = "123";    int total = 1000000;    std::chrono::time_point<std::chrono::system_clock> start = std::chrono::system_clock::now();    for (int i = 0; i < total; i++) {        int tmp = atoi(val.substr(1, 2).c_str());    }    std::chrono::time_point<std::chrono::system_clock> end = std::chrono::system_clock::now();    std::chrono::microseconds diff = std::chrono::duration_cast<std::chrono::microseconds>(end - start);    cout << "using substr:" << diff.count() << "ms" << endl;    start = std::chrono::system_clock::now();    for (int i = 0; i < total; i++) {        char vals[2] = { val[1],val[2] };        int tmp = atoi(vals);    }    end = std::chrono::system_clock::now();    diff = std::chrono::duration_cast<std::chrono::microseconds>(end - start);    cout << "using char[]:" << diff.count() << "ms" << endl;    return 0;}

执行后果

论断

应用字符间接结构，性能是substr的十倍左右