1. itoa
itoa是广泛应用的非标准c语言扩展函数,头文件为 #icnlude<stdlib.h>
char* itoa(int value,char* string,int radix);
#include<iostream>
#include<cstdlib>
using namespace std;
int main(){
	int i=15;
	char str[25];
	itoa(i,str,16);
	cout<<str<<endl;
	return 0;
}
2. sprintf
C的库函数,头文件#include<stdlib.h>
int sprintf( char *buffer, const char *format, [ argument] … );
#include<stdio.h>
#include<stdlib.h>
int main()
{
	char buffer[50];
	int n,a=5,b=3;
	n = sprintf(buffer,"%dplus%dis%d",a,b,a+b);
	printf("[ %s ] is a string %d chars long\n",buffer,n);/*“格式输出”*/
	 
	return 0;
}
3.atoi
C库函数,#icnlude<stdlib.h>
int atoi(const char *nptr);
#include<stdlib.h>
#include<stdio.h>
int main(void)
{
	double n;
	char*str="12345.67";
	n=atoi(str);
	printf("string=%s integer=%d\n",str,(int)n);
	return 0;
}
4. atoi的一个实现
#include <iostream>
using namespace std;
void main(void){
	char str[20];      
	int i,n=0;	
	cout<<"Enter the string:";         
	cin.getline(str,20,‘\n‘);
	
    for (i=0; str[i] != ‘\0‘; i++) 
		n = n*10+(str[i]-‘0‘);
	cout<<"Corresponding number is "<<n<<endl;
    cout<<"The digits of the number from low to high is ";
	while(n){
		cout<<n%10<<‘,‘;   
		n/=10;
	}
	cout<<endl;
}
原文:http://www.cnblogs.com/sjw1357/p/3836086.html