65. Valid Number--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.

符合规则的 [".1","01","1."  ,"-.1","+.8","46.e3",".2e81","1.431352e7"," 005047e+6","32.e-80123"]
不符合["e9","2e"," . " ," "]

正则表达式的解：

var isNumber = function(s) {
   return  !!s.match(/^\s*-?\d+\s*$|^\s*-?\d+\.\d*\s*$|^\s*-?\.\d+\s*$|^\s*-?\d*\.?\d+e-?\+?\d+\s*$|^\s*-?\d+\.?e-?\+?\d+\s*$|^\s*\+\d+\s*$|^\s*\+\d+\.\d*\s*$|^\s*\+\.\d+\s*$|^\s*\+\d*\.?\d+e-?\+?\d+\s*$|^\s*\+\d+\.?e-?\+?\d+\s*$/)
};//Runtime: 182 ms??????94.12%

LeetCode-Valid Number - 有限状态机

var isNumber = function(s) {
          var state={
              value:0,
              "0":[0,1,2,3],    //0 space start 开始的空白，后面可以接[0,1,2,3]种字符。开始的空白、正负、点前面的数字、点 
              "1":[2,3],        //1 +-          正负
              "2":[2,3,5,8],    //2 shuzi dot   点前面的数字
              "3":[4,5,8],      //3 dian        点
              "4":[4,5,8],      //4 dot shuzi   点后面的数字
              "5":[6,7],        //5 e           e
              "6":[7],          //6 e +-        e后面的正负
              "7":[7,8],        //7 e shuzi     e后面的数字
              "8":[8],          //8 space end   结尾的空白
              change:function(x){
                  for(var i in this[this.value]){
                      if(this[this.value][i]==x){
                          this.value=x;
                          return true;
                      }
                  }
                  return false;
              }
          };
          var isDian=false;
          var isE=false;
          var isStart=false;
          var   Num=0;
         for(var i=0;i< s.length;i++){
             if(s.charAt(i)==" "){
                 if(!isStart){
                     if(state.change(0)){continue}else{return false};
                 }else{
                     if(state.change(8)){continue}else{return false};
                 }
             }
             isStart=true;
             if(!!s.charAt(i).match(/\+|-/)){
                 if(isE){
                     if(state.change(6)){continue}else{return false};
                 }
                 if(state.change(1)){continue}else{return false};
             }
             if(!!s.charAt(i).match(/[0-9]{1}/)){
                 if(isE){
                     if(state.change(7)){continue}else{return false};
                 }
                 if(isDian){
                     Num++;
                     if(state.change(4)){continue}else{return false};
                 }
                 Num++;
                 if(state.change(2)){continue}else{return false};
             }
             if(s.charAt(i)=="."){
                 isDian=true;
                 if(state.change(3)){continue}else{return false};
             }
             if(s.charAt(i)=="e"){
                 isE=true;
                 if(state.change(5)){continue}else{return false};
             }else{
                 return false;
             }
         }
          if(Num<1){return false;}
         if( state[state.value][state[state.value].length-1]==8){
             return true;
         }
          else{return false;}
      };   //Runtime: 216 ms 76.47%

突然记起来一个js中自带的方法

var isNumber = function(s) {  
    if(s.match(/^\s*$/)){ return false;}
        return  !isNaN(s);
};   //Runtime: 180 ms超过94.12%