Problem
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.
Update (2015-02-10):
The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.
Solution
/**
* @param {string} s
* @return {boolean}
*/
var isNumber = function(s) {
var state = [
{},
{'blank': 1, 'sign': 2, 'digit':3, '.':4},
{'digit':3, '.':4},
{'digit':3, '.':5, 'e':6, 'blank':9},
{'digit':5},
{'digit':5, 'e':6, 'blank':9},
{'sign':7, 'digit':8},
{'digit':8},
{'digit':8, 'blank':9},
{'blank':9}
];
var validState = [3, 5, 8, 9];
var currentState = 1;
var len = s.length;
var str = '';
var type = '';
for (var i = 0; i < len; i++) {
str = s[i];
if (str >= '0' && str <= '9') {
type = 'digit';
} else if (str === '+' || str === '-') {
type = 'sign';
} else if (str === ' ') {
type = 'blank';
} else {
type = str;
}
if (state[currentState][type] === undefined) {
return false;
} else {
currentState = state[currentState][type];
}
}
if (validState.indexOf(currentState) === -1) {
return false;
} else {
return true;
}
};
Explain:
Complexity:
- Time complexity : O(n).
- Space complexity : O(1).