Interview Questions And Answers 
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Write a function that takes in a string parameter and checks to see whether or not it is an integer, and if it is then return the integer value.
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int str2int(const char *str)
{
int value = 0;
int sign = (str[0] == ‘-’)?-1:1;
int i = (str[0] == ‘-’)?1:0;
char ch;
while(ch = str[i++])
{
if ((ch >= ‘0′)&&(ch <= ‘9′))
value = value*10 + (ch - ‘0′);
else
return 0;
}
return value*sign;
}
#include <stdio.h>
int strtoint(char *s)
{
int index = 0, flag = 0;
while( *(s+index) != ‘ ’)
{
if( (*(s + index) >= ‘0′) && *(s + index) <= ‘9′)
{
flag = 1;
index++;
}
else
{
flag = 0;
break;
}
}
if( flag == 1 )
return atoi(s);
else
return 0;
}
main()
{
printf(”%d”,strtoint(”0123″));
printf(”n%d”,strtoint(”0123ii”));
}
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int returnInt ( string &str )
{
stringstream s ;
s << str;
int p;
if ( s >> p )
{
return p ;
}
else
{
//technically, this should throw an exception
cout << “Not A Number!”<< endl ;
return 0 ;
}
}
int main ()
{
string s;
cout << “input a #” << endl ;
getline (cin, s ) ;
int p = returnInt ( s ) ;
cout << p ;
return 0 ;
}
sigh,i love the power of the c++ standard libraries
private static int strToInt(String s){
int result=0;
for(int i=0;i
=’0′&& cyou guys haven’t heard of isDigit? It’s in standard ANSI C
You should also consider the output number to be bigger than 4gb, therefore you should test for length of string, and that the str[0] (or str[0] in case has a sign) is
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