方法一：//用數學函式#include<stdio.h>#include<math.h>void main(){int a;scanf("%d",&a);printf("%d\n",abs(a));}方法二：//判斷#include<stdio.h>void main(){int a;scanf("%d",&a);if(a>=0)printf("%d\n",a);elseprintf("%d\n",-a);}Problem Description求實數的絕對值。Input輸入資料有多組，每組佔一行，每行包含一個實數。輸入檔案直到EOF為止！Output對於每組輸入資料，輸出它的絕對值，要求每組資料輸出一行，結果保留兩位小數。Example Input123-234.00Example Output123.00234.00答案：#include <iostream>#include <cmath>#include <iomanip>using namespace std;int main(){double a;while(cin >> a){cout<< fixed <<setprecision(2) << abs(a) << endl;}return 0;}