【剑指offer】表示数值的字符串（字符串）

题目描述

请实现一个函数用来判断字符串是否表示数值（包括整数和小数）。例如，字符串"+100",“5e2”,"-123",“3.1416"和”-1E-16"都表示数值。 但是"12e",“1a3.14”,“1.2.3”,"±5"和"12e+4.3"都不是。

链接

https://www.nowcoder.com/practice/6f8c901d091949a5837e24bb82a731f2?tpId=13&tqId=11206&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

代码

class Solution {
public:
    bool isNumeric(char* string)
    {
        if(string == NULL){
            return false;
        }
        char *first = NULL, *second = NULL;
        int flagE = -1;
        for(int i = 0; i < strlen(string); i++){
            if(string[i] == 'e' || string[i] == 'E'){
                flagE = i;
            }
        }
        if(flagE == -1){
            return isNum(string);
        }
        else{
            first = (char*)malloc(sizeof(char) * (flagE + 1));
            second = (char*)malloc(sizeof(char) *(strlen(string) - flagE));
            int i, j;
            for(i = 0; i < flagE; i++){
                first[i] = string[i];
            }
            first[i] = '\0';
            for(i = 0, j = flagE+1; j < strlen(string); i++, j++){
                second[i] = string[j];
            }
            second[i] = '\0';
            return isNum(first) && isInt(second);
        }
    }
    bool isNum(char* string){
        if(string == NULL){
            return false;
        }
        bool flag = true;
        if(!(string[0] == '-' || string[0] == '+' || (string[0] > '0' && string[0] <= '9'))){
            flag = false;
        }
        bool xiaoshudian = false; // 表示是否已经有小数点
        for(int i = 1; i < strlen(string); i++){
            if(string[i] == '.' && string[i+1] == '\0'){
                flag = false;
                break;
            }
            else if(string[i] == '.' && xiaoshudian == false){
                xiaoshudian = true;
            }
            else if(string[i] == '.' && xiaoshudian == true){
                flag = false;
                break;
            }
            else if(string[i] >= '0' && string[i] <= '9'){
                continue;
            }
            else{
                flag = false;
                break;
            }
            if(string[i+1] == '\0'){
                break;
            }
        }
        return flag;
    }
    bool isInt(char* string){
        if(string == NULL){
            return false;
        }
        bool flag = true;
        if(!(string[0] == '-' || string[0] == '+' || (string[0] > '0' && string[0] <= '9'))){
            flag = false;
        }
        for(int i = 1; i < strlen(string); i++){
            if(string[i] >= '0' && string[i] <= '9'){
                continue;
            }
            else{
                flag = false;
                break;
            }
            if(string[i+1] == '\0'){
                break;
            }
        }
        return flag;
    }
};

标签：flagE,string,offer,数值,char,second,&&,字符串,first
来源： https://blog.csdn.net/u013095333/article/details/88600806