leetcode中字符串转化为数字

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8. String to Integer (atoi

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

fas

大概就是说，我们在字符串的前面可以加入空格，和数字的符号+-，然后数字中间不能有其它字符，代码如下

int myAtoi(char* str) {   if(*str==NULL)   return 0;   int res=0;   int sign=1;   int i=0;  while(isspace(*str)) str++;   if(str[0]=='-'){       sign=-1;       i++;   }   else if(str[0]=='+'){       sign=+1;       i++;   }else{       sign=+1;   }   while(str[i]>='0'&&str[i]<='9'){       if(res>INT_MAX/10||(res==INT_MAX/10&&str[i]-'0'>7)){           if(sign==1) return INT_MAX;           else return INT_MIN;       }       res=10*res+(str[i++]-'0');   }   return sign*res;    }

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