c - 为什么我的程序会跳过 switch 指令？

Question

我正在尝试编写一个程序，在用户输入 7 个 float 之后；它们被存储到一个数组中，然后像这样打印出来:

日值直方图
1 37.8 ***
2 40.6 *****

其中 Istogram 列中 * 的数量由 value - 34 给出。

我写了这段代码:

#include <stdio.h>
#define OBSERVATION 7
#define MEDIAN 34

int main() {
  float temp[OBSERVATION] = {0};

  printf("Insert the patient's temperature over the course of 7 days: ");
  for(int i = 1; i <= OBSERVATION; i++){
    scanf("%f", &temp[i]);
  }

  printf("DAY\tVALUE\tISTOGRAM\n");
  for(int i = 1; i <= OBSERVATION; i++){
    printf("%6d\t%6g\n", i, temp[i]);
  }
  for(int i = 1; i <= OBSERVATION; i++){
    switch ((int)temp[i] - MEDIAN) {
      case 0: break;
      case 1: printf("\t\t\t\t*");
              break;
      case 2: printf("\t\t\t\t**");
              break;
      case 3: printf("\t\t\t\t***");
              break;
      case 4: printf("\t\t\t\t****");
              break;
      case 5: printf("\t\t\t\t*****");
              break;
      case 6: printf("\t\t\t\t******");
              break;
      case 7: printf("\t\t\t\t*******");
              break;
      case 8: printf("\t\t\t\t********");
              break;
      case 9: printf("\t\t\t\t*********");
              break;
      case 10: printf("\t\t\t\t*********");
               break;
      case 11: printf("\t\t\t\t**********");
               break;
      case 12: printf("\t\t\t\t***********");
               break;
    }
    printf("\n");
  }

  return 0;
}

代码编译良好并正确输出前两列，但完全跳过 switch 语句。我已经尝试检查当它被转换为 int 时是否错误地将 0 分配给 temp[i]，但事实并非如此。不要那样做。它只是跳过开关。

您还有更“紧凑”的方式来打印 * 列而不使用 switch 吗？

Answer 1

我会像这样重写你的代码:

#include <stdio.h>
#include "math.h"
#define OBSERVATION 7
#define MEDIAN 34

int main() {
  float temp[OBSERVATION] = {0};
  int iDifference = 0;

  printf("Insert the patient's temperature over the course of 7 days: \n");
  for(int i = 0; i < OBSERVATION; i++){
    scanf("%f", &temp[i]);
  }

然后打印标题:

  printf("DAY\tVALUE\tISTOGRAM\n");

开始行循环:

  for(int i = 0; i < OBSERVATION; i++){
    // calculate the difference integer
    iDifference = round(temp[i] - MEDIAN);
    // don't add stars if the temperature diff is lower than 0
    if(iDifference < 0) iDifference = 0;
    // print the first two columns, notice that the new line isn't added yet
    printf("%6d\t%6.2f\t", i, temp[i]);
    // print the stars
    vDrawStars(iDifference);
    // then write the newline character
    printf("\n");
  }

  return 0;
}

然后画星星例程:

void vDrawStars(int prm_iCount){
    int p = 0;
    // I didn't understand the case for it but
    // printf("\t\t\t\t");
    // then draw the needed stars
    for(p = 0; p < prm_iCount; p++)
    {
        printf("*");
    }
    // no new lines, still on the same line.
}

这里有一个演示:https://onlinegdb.com/BJPyvDJRX