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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.
bool isNumber(string s) { int l = s.length(), i; bool flag=0, point[2]={0,0}, num[2]={0,0}; for(i=0; s[i] == ‘ ‘; i++); for(; i<l; i++) { if(s[i] == ‘ ‘) break; if(s[i] == ‘-‘ || s[i] == ‘+‘) { if(num[flag] == true || point[flag] == true) return false; } else if(isdigit(s[i])) num[flag] = true; else if(s[i] == ‘.‘) { if(point[flag] || flag == true) return false; point[flag] = true; } else if(s[i] == ‘e‘) { if(flag == 1) return false; if(num[0] == false) return false; flag = 1; } else return false; } for(;i<l;i++) { if(s[i]!=‘ ‘) return false; } if(!num[0] && !num[1]) return false; if(flag && !num[1]) return false; return true; }
测试用例：
"0e" -- false
". 1" -- false
"-1." -- true
".-4" -- false
"+.8" -- true
"6e6.5" -- false
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原文地址：http://www.cnblogs.com/argenbarbie/p/5270914.html
