Question

我想写一个从存储在char数组中的字符串中提取数字的函数。例如。输入：“141923adsfab321221.222”，我的函数应返回141923和321221.222。下面是我到目前为止，它运行和编译但它吐出完全不相关的数字，如48 49 50 51等，无论我如何改变输入。请帮忙。

#include <iostream>
#include <bits/stdc++.h>
using namespace std;
double GetDoubleFromString(char * str){
    static char * start;
    //starting point of the search
    if(str)
        start=str;
    //check if str is empty
    for (;*start&&!strchr("0123456789.",*start);++start);
    //jump thru chars that are not num related
    if (*start=='\0'){
        return -1;
    // check if at the end of the string
    }
    char *q=start;
    //mark the position of the start of a number
    for (;*start&&strchr("0123456789.",*start);++start);
    //jump thru chars that are num related
    if (*start){
        *start='\0';
        ++start;
    //as *start rest at a non num related char, mutate it to \0 and push forward
    }
    return *q;
    //I tried return (double) *q; but that does not work either and in the same way
}

int main(){
    char line[300];
    while(cin.getline(line,280)) {
        double n;
        n = GetDoubleFromString(line);
        while( n > 0) {
            cout << fixed << setprecision(6) << n << endl;
            n = GetDoubleFromString(NULL);
        }
    }
    return 0;
}

Answer 1

看起来您的数字分隔代码是正确的，但您错过了将字符数组['1', '4', '1', '9', '2', '3', '\0']转换为双141923的关键步骤。标准库具有专门为此目的而设计的函数std::atof。

你只需在返回时使用它：

return std::atof(q);

试图写函数试图从字符串中提取数字，但它返回不相关的数字

1 个答案: