如何使用C++將一系列整數轉換爲列表

Question

我有一個格式爲1,3-7,10,11-15, 的字符串輸入我想確定所有在該範圍內輸入的整數。我如何使用C++實現這一點？

TIA 顧比

Answer 1

此問題屬於解析的域。你會使用一個解析器。解析器解釋一種語言。在你的情況下，語言會看起來像這樣的事情：

input = comma-separated sequence of fragments 
fragment = integer or range 
range = integer-integer 
integer = sequence of digits 0..9 

Answer 2

//Disclaimer -- untested 
//Disclaimer -- this is not good code, but it's a quick and dirty way to do this 
//    if you're trying to see a possible solution. 

#include <algorithm> 
#include <functional> 
#include <vector> 

const char input[] = "1,3-7,10,11-15"; 
const char * inputBegin = input; 
const char * inputEnd = input + strlen(input); 
std::vector<int> result; 
for(; inputBegin < inputEnd; inputBegin = std::find_if(inputBegin, inputEnd, isdigit)) { 
    int first = *inputBegin - '0'; 
    for(inputBegin++; inputBegin < inputEnd && isdigit(*inputBegin); inputBegin++) 
     first = first * 10 + (*inputBegin - '0'); 
    int last = first; 
    if (++inputBegin < inputEnd && *inputBegin == '-') { 
     last = inputBegin - '0'; 
     for(inputBegin++; inputBegin < inputEnd && isdigit(*inputBegin); inputBegin++) 
      last = last * 10 + (*inputBegin - '0'); 
    } 
    for(; first < last; first++) 
     result.push_back(first); 
}