字串與數字的轉換（C ）

資料多的時候可能有點慢，不過很好用

string str =

"123"
;int num;
stringstream ss;
ss << str;
ss >> num;
cout << num << endl;

int num =

32.123
;	string str;
stringstream ss;
ss << num;
ss >> str;
//cout << ss.str() endl;一樣的效果
cout << str;

char str=

"123456"
;int num;
sscanf
(str,
"%d"
,&num)
;//這裡切換型別即可
cout << num << endl;

char str[10]

;int num =
123465
;sprintf
(str,
"%d"
,num)
;//想改變其他的只需改變這的型別
cout << str;

如：

//例項1

char str=
"171"
;int num;
sscanf
(str,
"%x"
,&num)
;	cout << num << endl;
//轉為了16進製制
//例項2
char str=
"ab"
;int num;
sscanf
(str,
"%x"
,&num)
;//16進製制轉為10進製，171
cout << num << endl;

char str=

"171"
;int num =
atoi
(str)
;	cout << num << endl;

函式原型：char *itoa(int value, char *string, int radix);

value為輸入整數，string為輸出轉換的字串，radix 為以幾進製輸出

int num =23;

char str[10]
;itoa
(num,str,10)
;	cout << str;

char p[20]

="hello world!"
;   		string str
(p);
cout << str;

string str=

"hello world"
;const
char
*c = str.
c_str()
;	cout << c << endl;

const

char
* tmp =
"hello world"
;char
* p =
const_cast
<
char
*>
(tmp)
;    cout << p << endl;

char

* p =
"hello world"
;const
char
* temp = p;
cout << temp << endl;

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