LeetCode String to Integer (atoi) 解题报告
任务是判断可能出现的情况:
1.空格
2.空指针
3.首字符是0
4.首字符是“+”或“-”
5.判断边界条件,上界INT_MAX=2147483647,下届INT_MIN=-2147483648,小心判断
1 // 2 // main.cpp 3 // Longest Substring 4 // 5 // Created by Bowie Hsu on 29/11/21. 6 // Copyright (c) 2014年 Bowie Hsu . All rights reserved. 7 // 8 9 #include <iostream> 10 #include <string> 11 #include <sstream> 12 #include <vector> 13 #include "stdio.h" 14 #include "ctype.h" 15 using namespace std; 16 17 class Solution { 18 public: 19 int atoi(const char *str) 20 { 21 int ibgn=1; 22 //判断字符串的情况,空格,空指针 23 while(*str==' ') 24 str++; 25 if(*str==0) 26 str++; 27 //str含有负号,输出的int为负 28 if(*str=='-') 29 { 30 ibgn=-1; 31 str++; 32 } 33 else if (*str=='+') 34 { 35 //ibgn=1; 36 str++; 37 } 38 int output=0; 39 while (isdigit(*str)) 40 { 41 int i=*str-'0'; 42 output=output*10+i; 43 ++str; 44 45 if (ibgn==1 && output>INT_MAX) 46 { 47 output=2147483647; 48 } 49 else if(ibgn==-1 && output*ibgn<INT_MIN) 50 { 51 output=2147483648; 52 } 53 } 54 return output*ibgn; 55 } 56 }; 57 int main() 58 { 59 const char abb='3'; 60 const char *input=&abb; 61 int ans; 62 Solution x; 63 ans=x.atoi(input); 64 cout<<ans<<endl; 65 //cout<<"what?"<<endl; 66 67 }