sscanf格式化輸入C++

Question

我有下面的代碼，如果輸入字符串中沒有空格，它的工作原理。

char* input2 = "(1,2,3)"; 
sscanf (input2,"(%d,%d,%d)", &r, &n, &p); 

這失敗以下輸入：

char input2 = " (1 , 2 , 3 ) "; 

如何解決這一問題？

Answer 1

簡單修復：在模式中添加空格。

char* input2 = "(1 , 2 , 3)"; 
sscanf (input2,"(%d, %d, %d)", &r, &n, &p); 

模式中的空格消耗任何數量的空白，所以你很好。測試程序：

 const char* pat="(%d , %d , %d)"; 
     int a, b, c; 

     std::cout << sscanf("(1,2,3)", pat, &a, &b, &c) << std::endl; 
     std::cout << sscanf("(1 , 2 , 3)", pat, &a, &b, &c) << std::endl; 
     std::cout << sscanf("(1, 2 ,3)", pat, &a, &b, &c) << std::endl; 
     std::cout << sscanf("( 1 , 2 , 3)", pat, &a, &b, &c) << std::endl; 

輸出：

3 
3 
3 
3 

此行爲是因爲從手動以下段落：

A directive is one of the following: 

·  A sequence of white-space characters (space, tab, newline, etc.; 
     see isspace(3)). This directive matches any amount of white space, 
     including none, in the input.