65. Valid Number

https://leetcode.com/problems/valid-number/discuss/23738/Clear-Java-solution-with-ifs

 

 

class Solution {
    public boolean isNumber(String s) {
        s = s.trim();
        
        boolean numberSeen = false, numberAfterE = false, eSeen = false, pointSeen = false;
        for(int i = 0; i < s.length(); i++){
            char c = s.charAt(i);
            if(c >= '0' && c <= '9'){
                numberSeen = true;
                numberAfterE = true;
            }else if(c == '.'){
                if(pointSeen || eSeen){
                    return false;
                }
                pointSeen = true;
            }else if(c == 'e'){
                if(eSeen || !numberSeen){
                    return false;
                }
                numberAfterE = false;
                eSeen = true;
            }else if(c == '+' || c == '-'){
                if(i != 0 && s.charAt(i-1) != 'e'){
                    return false;
                }
            }else{
                return false;
            }
        }
        return numberSeen && numberAfterE;
        
    }
}