int sprintf(char *str, const char *format, ...);
char c[10];
sprintf(c, "%d", 15); // 將整數(shù)轉(zhuǎn)換成字符串

//浮點數(shù)轉(zhuǎn)字符串，number為要轉(zhuǎn)換的數(shù)，ndigit表示要轉(zhuǎn)換的位數(shù)
char *gcvt(double number, int ndigit, char *buf);
//浮點數(shù)轉(zhuǎn)字符串，number為要轉(zhuǎn)換的數(shù)，ndigit表示要轉(zhuǎn)換的位數(shù)， decpt和sign為輸出參數(shù)，decpt為小數(shù)點位
//數(shù)，sign為符號。返回轉(zhuǎn)換后的字符串，不含符號和小數(shù)點。
char *ecvt(double number, int ndigits, int *decpt, int *sign);
//fcvt與ecvt不同在于fcvt的ndigit參數(shù)表示小數(shù)點后的長度
char *fcvt(double number, int ndigits, int *decpt, int *sign); 

int sscanf(const char *str, const char *format, ...);
char str[] = "15.455";
int i;
float fp;
sscanf( str, "%d", &i ); // 將字符串轉(zhuǎn)換成整數(shù) i = 15
sscanf( str, "%f", &fp ); // 將字符串轉(zhuǎn)換成浮點數(shù) fp = 15.455000

int atoi(const char *nptr);
long atol(const char *nptr);
long long atoll(const char *nptr);


double strtod(const char *nptr, char **endptr);
float strtof(const char *nptr, char **endptr);
long double strtold(const char *nptr, char **endptr);
long int strtol(const char *nptr, char **endptr, int base);
long long int strtoll(const char *nptr, char **endptr, int base);
unsigned long int strtoul(const char *nptr, char **endptr, int base);
unsigned long long int strtoull(const char *nptr, char **endptr, int base);

string to_string (int val);
string to_string (long val);
string to_string (long long val);
string to_string (unsigned val);
string to_string (unsigned long val);
string to_string (unsigned long long val);
string to_string (float val);
string to_string (double val);
string to_string (long double val)

//1. 調(diào)string的data函數(shù)
string s = "abc";  //data函數(shù)不會加結(jié)束符'\0' c_str會加
char *p = s.data();

//2. 調(diào)string的c_str函數(shù)
string s = "abc";
char *p = s.c_str();

//3. 調(diào)string的copy函數(shù)
string s = "abc";
char p[10];
s.copy(p, 3, 0); //復(fù)制3個字符，從0位置開始
p[3] = '\0';  //需要手動加結(jié)束符

string s;
char *p = "123";
s = p; //直接復(fù)制即可