LeetCode 65. Valid Number

 65. Valid Number

Validate if a given string is numeric.

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

AC代码：

bool isNumber(string s) { int size=s.size(); if(size==0) return false; int start=0,end=size-1; while(s[start]==' '){ start++; } while(s[end]==' '){ end--; } bool hasPoint=false,hasNum=false,hasE=false; for(int i=start;i<=end;i++){ if(s[i]=='.'){ if(hasPoint||hasE){ return false; } hasPoint=true; } else if(s[i]=='e'){ if(hasE||!hasNum){ return false; } hasE=true; } else if(s[i]<'0'||s[i]>'9'){ if(i==start&&(s[i]=='+'||s[i]=='-')){ continue; } else if(i>0&&s[i-1]=='e'&&(s[i]=='+'||s[i]=='-')){ continue; } else{ return false; } } else { hasNum=true; } } if(s[end]=='e'||s[end]=='-'||s[end]=='+') return false; if(!hasNum&&hasPoint) return false; if(end==-1) return false; return true; }