【leetcode】Valid Number
最近使用开发的过程中出现了一个小问题,顺便记录一下原因和方法--
Question :
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.
Anwser 1 :
class Solution { public: bool isNumber(const char *s) { // Start typing your C/C++ solution below // DO NOT write int main() function if (s == NULL) return false; while(isspace(*s)) s++; if (*s == '+' || *s == '-') s++; bool eAppear = false; bool dotAppear = false; bool firstPart = false; bool secondPart = false; bool spaceAppear = false; while(*s != '\0') { if (*s == '.') { if (dotAppear || eAppear || spaceAppear) return false; else dotAppear = true; } else if (*s == 'e' || *s == 'E') { if (eAppear || !firstPart || spaceAppear) return false; else eAppear = true; } else if (isdigit(*s)) { if (spaceAppear) return false; if (!eAppear) firstPart = true; else secondPart = true; } else if (*s == '+' || *s == '-') // behind of e/E { if (spaceAppear) return false; if (!eAppear || !(*(s-1) == 'e' || *(s-1) == 'E')) return false; } else if (isspace(*s)) spaceAppear = true; else return false; s++; } if (!firstPart) { return false; } else if (eAppear && !secondPart) { return false; } return true; } };
Anwser 2 :
class Solution { public: bool isNumber(const char *s) { // Start typing your C/C++ solution below // DO NOT write int main() function int mat[11][7] = { 0 ,0 ,0 ,0 ,0 ,0 ,0, // false 0 ,2 ,3 ,0 ,1 ,4 ,0, // 1 0 ,2 ,5 ,6 ,9 ,0 ,10, // 2 0 ,5 ,0 ,0 ,0 ,0 ,0, // 3 0 ,2 ,3 ,0 ,0 ,0 ,0, // 4 0 ,5 ,0 ,6 ,9 ,0 ,10, // 5 0 ,7 ,0 ,0 ,0 ,8 ,0, // 6 0 ,7 ,0 ,0 ,9 ,0 ,10, // 7 0 ,7 ,0 ,0 ,0 ,0 ,0, // 8 0 ,0 ,0 ,0 ,9 ,0 ,10, // 9 10,10,10,10,10,10,10 // 10 }; int i = 0; int stat = 1; while(s[i] != '\0') { int type = 0; if(s[i] >= '0' && s[i] <= '9') type = 1; else if(s[i] == '.') type = 2; else if(s[i] == 'e') type = 3; else if(s[i] == ' ') type = 4; else if(s[i] == '+' || s[i] == '-') type = 5; if(stat == 0) return false; stat = mat[stat][type]; i++; } stat = mat[stat][6]; if(stat == 10) { return true; } return false; } };
参考推荐:
文章结束给大家分享下程序员的一些笑话语录:
刹车失灵
有一个物理学家,工程师和一个程序员驾驶着一辆汽车行驶在阿尔卑斯山脉 上,在下山的时候,忽然,汽车的刹车失灵了,汽车无法控制地向下冲去, 眼看前面就是一个悬崖峭壁,但是很幸运的是在这个悬崖的前面有一些小树 让他们的汽车停了下来, 而没有掉下山去。 三个惊魂未定地从车里爬了出来。
物理学家说, “我觉得我们应该建立一个模型来模拟在下山过程中刹车片在高 温情况下失灵的情形”。
工程师说, “我在车的后备厢来有个扳手, 要不我们把车拆开看看到底是什么 原因”。
程序员说,“为什么我们不找个相同的车再来一次以重现这个问题呢?”