快速矩形交叉

问题描述

如果有两个矩形相交，什么是快速测试？

What's a fast way to test if 2 rectangles are intersecting?

一个线程（WOOT！），但我不明白如何写在Javascript中，它似乎是以古代形式的C ++写的。

A search on the internet came up with this one-liner (WOOT!), but I don't understand how to write it in Javascript, it seems to be written in an ancient form of C++.

struct
{
    LONG    left;
    LONG    top;
    LONG    right;
    LONG    bottom;
} RECT;

bool IntersectRect(const RECT * r1, const RECT * r2)
{
    return ! ( r2->left > r1->right
        || r2->right < r1->left
        || r2->top > r1->bottom
        || r2->bottom < r1->top
        );
}

推荐答案

翻译成JavaScript。请注意，您的代码中有一个错字，在文章的错误，如评论建议。特别地， r2->右侧应该是 r2-> r1-> left 和 r2-> bottom top 应为 r2-> bottom< r1> top 函数的工作。

This is how that code can be translated to JavaScript. Note that there is a typo in your code, and in that of the article, as the comments have suggested. Specifically r2->right left should be r2->right < r1->left and r2->bottom top should be r2->bottom < r1->top for the function to work.

function intersectRect(r1, r2) {
  return !(r2.left > r1.right ||
           r2.right < r1.left ||
           r2.top > r1.bottom ||
           r2.bottom < r1.top);
}

测试用例：

var rectA = {
  left:   10,
  top:    10,
  right:  30,
  bottom: 30
};

var rectB = {
  left:   20,
  top:    20,
  right:  50,
  bottom: 50
};

var rectC = {
  left:   70,
  top:    70,
  right:  90,
  bottom: 90
};

intersectRect(rectA, rectB);  // returns true
intersectRect(rectA, rectC);  // returns false

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