8.c

#include<stdio.h>
#include<stdint.h>

intmyAtoi(char*str) {
int64_tret=0;
intsign=1;
char*p=str;
/* ignore white spaces */
while (*p==' ') p++;

if (*p=='-') {
sign=-1;
p++;
 }
elseif (*p=='+') {
sign=1;
p++;
 }

while (*p >= '0'&&*p <= '9') {
ret=ret*10+ (*p-'0');
if (ret-1>INT32_MAX) ret= (int64_t)INT32_MAX+1;
//printf("%ld\n", ret);
p++;
 }

if (sign==-1) ret=-ret;
if (ret>INT32_MAX) ret=INT32_MAX;
if (ret<INT32_MIN) ret=INT32_MIN;

return (int)ret;
}

intmain() {
char*s[12];
s[0] =" 123 ";
s[1] ="123.4";
s[2] ="-1234";
s[3] ="2147483646";
s[4] ="2147483647";
s[5] ="2147483648";
s[6] ="-2147483647";
s[7] ="-2147483648";
s[8] ="-2147483649";
s[9] ="-1";
s[10] ="+-2";
s[11] ="9223372036854775809";

inti;
for (i=0; i<12; i++)
printf("%d\n", myAtoi(s[i]));

return0;
}