Valid Number ( Java )

LeetCode

Validate if a given string is numeric.

Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true

Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.

This is really a trivial question, a lot of corner cases need to be found, just like the Stirng to Integer question.

	/*
	Validate if a given string is numeric.
	Some examples:
	"0" => true
	" 0.1 " => true
	"abc" => false
	"1 a" => false
	"2e10" => true
	Note: It is intended for the problem statement to be ambiguous.
	You should gather all requirements up front before implementing one.
	*/
	public class ValidNumber {
	public boolean isNumber(String s) {
	if (s==null ){
	return false;
	}
	// trim off head and tail zeros which not affect result depend on question
	s=s.trim();
	if(s.length()==0){
	return false;
	}
	boolean hasNum=false;
	boolean canSign=true;
	boolean canDot=true;
	boolean canE=false;
	boolean hasE=false;
	int i=0;
	while(i<s.length()){
	char c=s.charAt(i++);
	if (c==' '){
	return false;
	}
	if (c=='+' ||c=='-'){
	if (!canSign){
	return false;
	}
	canSign=false;
	continue;
	}
	if (c=='.'){
	if (!canDot){
	return false;
	}
	canDot=false;
	canSign=false;
	continue;
	}
	if (c=='e'){
	if (!canE||hasE){
	return false;
	}
	canE=false;
	hasE=true;
	hasNum=false;
	canDot=false;
	canSign=true;
	continue;
	}
	if (c>='0' && c<='9'){
	hasNum=true;
	if (!canE&&!hasE){
	canE=true;
	}
	canSign=false;
	}
	else{
	return false;
	}
	}
	return hasNum;
	}
	}

view raw ValidNumber.java hosted with ❤ by GitHub