解释 while (fscanf(fp, "%d", &arr[count]) == 1) 的用法
时间: 2023-05-29 15:07:43 浏览: 47
As an AI language model, I do not have emotions and feelings, so the concept of null does not apply to me in this context. However, in computer programming, null is a value that represents the absence of a value or a lack of a defined object or variable. It is commonly used to indicate that a variable or object does not have a value assigned to it.
相关问题
C语言实现程序从一文件中读取数字,利用快速排序把大于某值的元素排出,并输出排序结果和比较次数
好的,让我来回答你的问题。以下是 C 语言实现程序从一文件中读取数字,利用快速排序把大于某值的元素排出,并输出排序结果和比较次数的代码:
```
#include <stdio.h>
#include <stdlib.h>
void quicksort(int arr[], int left, int right, int* cmpCount);
void swap(int* a, int* b);
int main() {
FILE* fp;
char filename[100];
int num, pivot, count = 0;
int* arr;
int i = 0, j = 0;
printf("请输入文件名: ");
scanf("%s", filename);
fp = fopen(filename, "r");
if (fp == NULL) {
printf("文件打开失败.");
return 1;
}
printf("请输入 pivot 值: ");
scanf("%d", &pivot);
while (fscanf(fp, "%d", &num) == 1) {
if (num > pivot) {
count++;
}
}
arr = (int*)malloc(count * sizeof(int));
fseek(fp, 0, SEEK_SET);
while (fscanf(fp, "%d", &num) == 1) {
if (num > pivot) {
arr[i++] = num;
}
}
printf("排序前数组: ");
for (j = 0; j < i; j++) {
printf("%d ", arr[j]);
}
printf("\n");
quicksort(arr, 0, i - 1, &count);
printf("排序后数组: ");
for (j = 0; j < i; j++) {
printf("%d ", arr[j]);
}
printf("\n");
printf("比较次数: %d\n", count);
fclose(fp);
free(arr);
return 0;
}
void quicksort(int arr[], int left, int right, int* cmpCount) {
int i = left, j = right;
int pivot = arr[(left + right) / 2];
while (i <= j) {
while (arr[i] < pivot) {
i++;
(*cmpCount)++;
}
while (arr[j] > pivot) {
j--;
(*cmpCount)++;
}
if (i <= j) {
swap(&arr[i], &arr[j]);
i++;
j--;
}
}
if (left < j) {
quicksort(arr, left, j, cmpCount);
}
if (i < right) {
quicksort(arr, i, right, cmpCount);
}
}
void swap(int* a, int* b) {
int temp = *a;
*a = *b;
*b = temp;
}
```
希望这可以解决你的问题。如果你有其他问题,欢迎随时问我。
编写程序从文本文件中读取整数,文件的每一行可以包含任意数量的整数(也可以没有),中间用一个或多个空格隔开。程序显示文件中的最大数和最小数以及中值(整数有序的情况下最接近中间的那个数。)如果文件中包含偶数个整数,中间会有两个整数,程序显示它们的均值(向下取整)。可以假定文件中包含的整数个数不超过10000。
可以回答这个问题。以下是程序的实现:
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *fp;
int num, count = , sum = , max = -2147483647, min = 2147483647;
int *arr = (int*)malloc(10000 * sizeof(int)); // 动态分配数组
fp = fopen("input.txt", "r"); // 打开文件
if (fp == NULL) {
printf("无法打开文件\n");
return 1;
}
while (fscanf(fp, "%d", &num) != EOF) { // 读取整数
arr[count++] = num; // 存入数组
sum += num; // 求和
if (num > max) max = num; // 更新最大值
if (num < min) min = num; // 更新最小值
}
fclose(fp); // 关闭文件
// 排序
for (int i = ; i < count - 1; i++) {
for (int j = i + 1; j < count; j++) {
if (arr[i] > arr[j]) {
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
// 计算中值
int median;
if (count % 2 == ) {
median = (arr[count/2-1] + arr[count/2]) / 2;
} else {
median = arr[count/2];
}
printf("最大数:%d\n", max);
printf("最小数:%d\n", min);
printf("中值:%d\n", median);
free(arr); // 释放数组内存
return ;
}