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[leetcode] Valid Number
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.
https://oj.leetcode.com/problems/valid-number/
思路1：直接处理，一般思路按照‘.’分开整数和小数，然后各自判断，情况略复杂。
思路2：自动机，建立好转移函数，代码很直观易懂。
思路3（偷懒）：直接写正则表达式（其实正则的匹配背后也是自动机）。
public class Solution { public boolean isNumber(String s) { if (s.trim().isEmpty()) { return false; } String regex = "[-+]?(\\d+\\.?|\\.\\d+)\\d*(e[-+]?\\d+)?"; if (s.trim().matches(regex)) { return true; } else { return false; } } public static void main(String[] args) { System.out.println(new Solution().isNumber("0")); System.out.println(new Solution().isNumber("0.1")); System.out.println(new Solution().isNumber(".1")); System.out.println(new Solution().isNumber("0.")); System.out.println(new Solution().isNumber(".")); System.out.println(new Solution().isNumber("abc")); System.out.println(new Solution().isNumber("1 a")); System.out.println(new Solution().isNumber("2e10")); }}
参考：
http://jane4532.blogspot.com/2013/09/valid-numberleetcode.html
http://www.cnblogs.com/chasuner/p/validNumber.html
http://leetcodenotes.wordpress.com/2013/11/23/leetcode-valid-number/
http://codeganker.blogspot.com/2014/04/valid-number-leetcode.html
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