1.字符串→整型
[cpp]
int atoi(char s[])
{
int i,n,sign;
for(i=0;isspace(s[i]);i++)//skip front spaces
;
sign=(s[i]=='-')? -1:1;
if(s[i]=='+'||s[i]=='-') //skip the sign
i++;
for(n=0;isdigit(s[i]);i++)
n=n*10+(s[i]-'0');
return sign*n;
}
2.整型→字符串
[cpp]
void itoa(int n,char s[])
{
int i,sign;
if((sign=n)<0)
n=-n;
i=0;
do{
s[i++]=n%10+'0';
}while((n/=10)>0);
if(sign<0)
s[i++]='-';
s[i]='\0';
reverse(s);
}
void reverse(char s[])
{
int c,i,j;
for(i=0,j=strlen(s)-1;i<j;i++,j--){
c=s[i];
s[i]=s[j];
s[j]=c;
}
}
3.字符串→浮點
[cpp]
//atof:translate string into double float
double atof(char s[])
{
double val,power;
int i,sign;
for(i=0;isspace(s[i]);i++)//skip space
;
sign=(s[i]=='-')?-1:1;
if(s[i]=='+'||s[i]=='-')
i++;
for(val=0.0;isdigit(s[i]);i++)
val=val*10.0+(s[i]-'0');
if(s[i]=='.')
i++;
for(power=1.0;isdigit(s[i]);i++){
val=10.0*val+(s[i]-'0');
power*=10.0;
}
return sign*val/power
