这道题是什么回事，能写一下吗

图片太模糊了，大体代码如下：

#include <stdio.h>

int main()
{
    int f,x,a;
    scanf("%d",&x);
    if(x<0)
        a = -1;
    else if(x == 0)
        a = 0;
    else
        a = 1;
    switch(a)
    {
    case -1:
        f = -1;
        break;
    case 0:
        f = 0;
        break;
    case 1:
        f = 2;
        break;
    }
    printf("%d",f);
    return 0;
}

int main()
{
      float x,y;
      scanf("%f",&x);
      if(x>0)
          y = 2*x;
      else if(x==0)
          y=0;
      else
          y = -1;
      printf("%f",y);
      return 0;
}

用switch-case

#include<iostream>
using namespace std;
int main()
{
    float x = 0.0f;
    float fx =0.0f;
    cin >> x;
    int flag;
    if(x>0)
        flag=1;
    else if(x<0)
        flag = -1;
    else
        flag = 0;
    switch(flag){        //switch-case
        case 1 :
            fx = 2*x;
            break;
        case -1 :
            fx = -1;
            break;
        case 0:
            fx =0;
            break;       
    }
    cout<<"fx="<<fx;
    return 0;
}