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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.
1 class Solution { 2 public: 3 int myAtoi(string str) { 4 long long cur=0; 5 int num=0,i=0; 6 int flag1=0,flag2=0; 7 while(str[i]!=‘\0‘ && str[i]==‘ ‘) i++; 8 if(str[i]==‘-‘) flag1++,i++; 9 else if(str[i]==‘+‘) flag2++,i++; 10 for(; str[i]!=‘\0‘; i++) 11 { 12 if(str[i]>=‘0‘ && str[i]<=‘9‘) 13 { 14 if(flag1==2) 15 { 16 cur=cur*10-(str[i]-‘0‘); 17 if(cur<-2147483648) return -2147483648; 18 } 19 else if(flag1==1) cur=-str[i]+‘0‘,flag1++; 20 else 21 { 22 cur=cur*10+(str[i]-‘0‘); 23 if(cur>2147483647) return 2147483647; 24 } 25 } 26 else break; 27 } 28 num=(int)cur; 29 return num; 30 } 31 };
LeeCode-String to Integer (atoi)
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原文地址：http://www.cnblogs.com/vpoet/p/4659432.html
