一、先看题目
使用一个文本文件存储一组数据（x），编程读取数据并计算y=1/(200-x)的值，显示并保存结果，如果是非法操作，输出“Error”。
具体要求：
1 输入数据要典型，有代表性，输入数据类型为float。
2 能够处理错误输入数据，并输出“Error”。
3 使用文本文件作为程序的输入和输出。
文件读写参考：
打开文件
fp=fopen("input.txt","r");
错误判断
if(fp==NULL){printf("Not SUCH A FILE:%s",af);getch();return;
}
读入数据
fscanf(fp,"%d",&num);
fscanf(fp,"%f,%d",&x[i],&y[i]);
打开文件（写文件）
fp=fopen("result.txt","w");
写数据
fprintf(fp,"%d,%.2f,%d,%.2f\n",i,x[i],y[i],b[i]);
下面是程序
#include <iostream>
#include <cstdio>int writeToFile(int n, FILE *f);
float fx(float x);int main() {const int N = 100;// 打开文件并写入数据FILE *f = fopen("./input.txt", "w");if (f == NULL) {std::cerr << "Failed to open input file for writing!" << std::endl;return 1;}if (writeToFile(N, f) != 0) {std::cerr << "Error writing to file!" << std::endl;return 1;}// 打开文件并读取数据FILE *fin = fopen("./input.txt", "r");if (fin == NULL) {std::cerr << "Failed to open input file for reading!" << std::endl;return 1;}FILE *fout = fopen("./output.txt", "w");if (fout == NULL) {std::cerr << "Failed to open output file!" << std::endl;fclose(fin);return 1;}// 动态分配数组float *x = new float[N];float *y = new float[N];// 读取文件内容并计算for (int i = 0; i < N; i++) {fscanf(fin, "%f", &x[i]);y[i] = fx(x[i]);}// 将结果写入输出文件for (int i = 0; i < N; i++) {fprintf(fout, "%f\t%f\n", x[i], y[i]);}// 关闭文件并释放内存fclose(fin);fclose(fout);delete[] x;delete[] y;return 0;
}// 向文件中写数据
int writeToFile(int n, FILE *f) {if (f == NULL) {std::cerr << "Not SUCH A FILE !" << std::endl;return 1;}for (float x = 0; x < n; x++) { fprintf(f, "%f\n", x);}fclose(f);return 0;
}// 定义函数 f(x)
float fx(float x) {if (x == 200) {fprintf(stderr, "Error: division by zero\n");return -1;} else {return 1 / (200 - x);}
}
