題目來源:
http://blog.163.com/prevBlogPerma.do?host=zhedahht&srl=25411174200731139971&mode=prev
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<limits.h>
/*
* #define INT_MAX 2147483647
* #define INT_MIN (-INT_MAX-1)
*/
enum Status {
Success,
Fail
};
enum Status ret;
int negative;
int
Str2Int(const char *input)
{
long long num = 0;
negative = 0;
ret = Fail;
if(input == NULL)
return num;
const char *ptr = input;
if(*ptr=='+' || *ptr=='-') {
if(*ptr == '-')
negative = 1;
++ptr;
}
while(*ptr) {
if(!(*ptr>='0' && *ptr<='9'))
return num;
if((!negative && num>INT_MAX) || (negative && (-num)<INT_MIN))
return num;
num = num*10 + (*ptr-'0');
++ptr;
}
ret = Success;
return num;
}
#define MAX_LEN 101
int
main(int argc, char **argv)
{
int result;
char value[MAX_LEN];
while(scanf("%s", value) != EOF) {
result = Str2Int(value);
if(ret == Success)
printf("%d\n", negative ? (-result) : result);
else
printf("Invalid\n");
}
return 0;
}