codeforces 227 A 三角形的有向面积

本文提供 CodeForces 227A 题目“WheredoITurn?”的详细解析及解答思路。该题目要求根据三个坐标点判断英雄前往龙巢的方向,包括直行、左转或右转。文章通过示例说明了如何使用输入数据确定方向。

http://codeforces.com/problemset/problem/227/A

A. Where do I Turn?
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

Trouble came from the overseas lands: a three-headed dragon Gorynych arrived. The dragon settled at point C and began to terrorize the residents of the surrounding villages.

A brave hero decided to put an end to the dragon. He moved from point A to fight with Gorynych. The hero rode from point A along a straight road and met point B on his way. The hero knows that in this land for every pair of roads it is true that they are either parallel to each other, or lie on a straight line, or are perpendicular to each other. He also knows well that points B and C are connected by a road. So the hero must either turn 90 degrees to the left or continue riding straight ahead or turn 90 degrees to the right. But he forgot where the point C is located.

Fortunately, a Brave Falcon flew right by. It can see all three points from the sky. The hero asked him what way to go to get to the dragon's lair.

If you have not got it, you are the falcon. Help the hero and tell him how to get him to point C: turn left, go straight or turn right.

At this moment the hero is believed to stand at point B, turning his back to point A.

Input

The first input line contains two space-separated integers xa, ya (|xa|, |ya| ≤ 109) — the coordinates of point A. The second line contains the coordinates of point B in the same form, the third line contains the coordinates of point C.

It is guaranteed that all points are pairwise different. It is also guaranteed that either point B lies on segment AC, or angle ABC is right.

Output

Print a single line. If a hero must turn left, print "LEFT" (without the quotes); If he must go straight ahead, print "TOWARDS" (without the quotes); if he should turn right, print "RIGHT" (without the quotes).

Sample test(s)
input
0 0
0 1
1 1
output
RIGHT
input
-1 -1
-3 -3
-4 -4
output
TOWARDS
input
-4 -6
-3 -7
-2 -6
output
LEFT
Note

The picture to the first sample:

The red color shows points A, B and C. The blue arrow shows the hero's direction. The green color shows the hero's trajectory.

The picture to the second sample:


#include <stdio.h>
#include <iostream>
using namespace std;
double a,b,c,d,e,f;
int main()
{
    while(~scanf("%lf%lf%lf%lf%lf%lf",&a,&b,&c,&d,&e,&f))
    {
        double sum=a*d+e*b+c*f-e*d-a*f-c*b;
        cout << sum << endl;
        if(sum==0)
           printf("TOWARDS\n");
        else if(sum<0)
           printf("RIGHT\n");
        else
           printf("LEFT\n");
    }
    return 0;
}


### 关于 Codeforces Problem 1804A 的解决方案 Codeforces 是一个广受欢迎的在线编程竞赛平台,其中问题 1804A 可能涉及特定算法或数据结构的应用。尽管未提供具体题目描述,但通常可以通过分析输入输出样例以及常见解法来推导其核心逻辑。 #### 题目概述 假设该问题是关于字符串处理、数组操作或其他基础算法领域的内容,则可以采用以下方法解决[^2]: 对于某些初学者来说,遇到不熟悉的语言(如 Fortran),可能会感到困惑。然而,在现代竞赛环境中,大多数情况下会使用更常见的语言(C++、Python 或 Java)。因此,如果题目提及某种神秘的语言,可能只是为了增加趣味性而非实际需求。 #### 解决方案思路 以下是基于一般情况下的潜在解答方式之一: ```cpp #include <bits/stdc++.h> using namespace std; int main(){ int t; cin >> t; // 输入测试用例数量 while(t--){ string s; cin >> s; // 获取每组测试数据 // 假设这里需要执行一些简单的变换或者判断条件... bool flag = true; // 初始化标志位为真 for(char c : s){ if(c != 'a' && c != 'b'){ flag = false; break; } } cout << (flag ? "YES" : "NO") << "\n"; // 输出结果 } return 0; } ``` 上述代码片段展示了一个基本框架,适用于许多入门级字符串验证类问题。当然,这仅作为示范用途;真实场景下需依据具体要求调整实现细节。 #### 进一步探讨方向 除了官方题解外,社区论坛也是获取灵感的好地方。通过阅读他人分享的经验教训,能够加深对该类型习题的理解程度。同时注意积累常用技巧并灵活运用到不同场合之中[^1]。
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