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 requiremen…

LeetCode-String to Integer (atoi)

C++:
class Solution {
public:
    int atoi(const char *str) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        bool negative=false;
        while(*str==' ') str++;
        if(*str=='-'){
            negative=true;
            str++;
        }
        if(*str=='+') str++;
        long long res=0;
        while(*str!='\0'){
            if(*str>='0'&&*str<='9')
                res =res*10+*str-'0';
            else break;
            str++;
        }
        res =negative?-res:res;
        if(res>INT_MAX) return INT_MAX;
        if(res<INT_MIN) return INT_MIN;
        return res;
    }
};
Java:
public class Solution {
    public int atoi(String str) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if(str==null||str.length()==0) return 0;
        char[] ch=str.toCharArray();
        boolean negative=false;
        int index=0;
        while(ch[index]==' ') index++;
        if(ch[index]=='-'){
            negative=true;
            index++;
        }
        if(ch[index]=='+') index++;
        long res=0;
        while(index<ch.length){
            if(ch[index]>='0'&&ch[index]<='9'){
                res =res*10+ch[index]-'0';
                index++;
            }else break;
        }
        res=negative?-res:res;
        if(res>Integer.MAX_VALUE) return Integer.MAX_VALUE;
        if(res<Integer.MIN_VALUE) return Integer.MIN_VALUE;
        return (int)res;
    }
}