f.cpp

// Problem F: Three Sides Make A Triangle
// Author: Christopher Vo

#include <cstdio>
#include <cmath>
#define TOLERANCE 0.01
#define swap(a,b,c) {c t=a; a=b; b=t;}

double len(double x1, double y1, double x2, double y2)
{
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

bool eq(double a, double b)
{
  return (a < b + TOLERANCE) && (a > b - TOLERANCE);
}

int main()
{
  double x1, y1, x2, y2, x3, y3;
  while (fscanf(stdin, "%lf%lf%lf%lf%lf%lf", &x1, &y1, &x2, &y2, &x3, &y3) == 6) {
    double a = len(x1, y1, x2, y2);
    double b = len(x2, y2, x3, y3);
    double c = len(x3, y3, x1, y1);
    if (a > c)
      swap(c, a, double);
    if (b > c)
      swap(c, b, double);

    // co-linear?
    if (eq(c, a + b)) {
      puts("Not a Triangle");
      continue;
    }

    // classify sides
    if (eq(a, b) && eq(b, c))
      fputs("Equilateral ", stdout);
    else if (eq(a, b) || eq(b, c) || eq(a, c))
      fputs("Isoceles ", stdout);
    else
      fputs("Scalene ", stdout);

    // classify angles
    double c2 = c * c;
    double a2b2 = a * a + b * b;
    if (eq(c2, a2b2))
      puts("Right");
    else if (c2 < a2b2)
      puts("Acute");
    else
      puts("Obtuse");
  }
  puts("End of Output");
  return 0;
}

f.java

// Problem F: Three Sides Make A Triangle
// Author: Christopher Vo

import java.util.*;
import java.io.*;

public class F {

  static final double TOLERANCE = 0.01;

  static double len(double x1, double y1, double x2, double y2) {
    return Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  }

  static boolean eq(double a, double b) {
    return (a < b + TOLERANCE) && (a > b - TOLERANCE);
  }

  public static void main(String args[]) throws Exception {
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    PrintStream out = System.out;
    while (true) {
      StringTokenizer st = new StringTokenizer(in.readLine().trim());
      if (st.countTokens() != 6)
        break;
      double x1 = Double.parseDouble(st.nextToken());
      double y1 = Double.parseDouble(st.nextToken());
      double x2 = Double.parseDouble(st.nextToken());
      double y2 = Double.parseDouble(st.nextToken());
      double x3 = Double.parseDouble(st.nextToken());
      double y3 = Double.parseDouble(st.nextToken());
      double a = len(x1, y1, x2, y2);
      double b = len(x2, y2, x3, y3);
      double c = len(x3, y3, x1, y1);
      if (a > c) {
        double t = c;
        c = a;
        a = t;
      }
      if (b > c) {
        double t = c;
        c = b;
        b = t;
      }

      // co-linear?
      if (eq(c, a + b)) {
        out.println("Not a Triangle");
        continue;
      }

      // classify sides
      if (eq(a, b) && eq(b, c))
        out.print("Equilateral ");
      else if (eq(a, b) || eq(b, c) || eq(a, c))
        out.print("Isoceles ");
      else
        out.print("Scalene ");

      // classify angles
      double c2 = c * c;
      double a2b2 = a * a + b * b;
      if (eq(c2, a2b2))
        out.println("Right");
      else if (c2 < a2b2)
        out.println("Acute");
      else
        out.println("Obtuse");
    }
    out.println("End of Output");
  }
}