Radar Detection

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- Tag: #array

There is a bunch of radars on a 2D plane(Radar has x, y coordinates, and a radius r which is the range can be detected). Now, there is a car that passes through the range of y = 0 and y = 1 and cannot be detected by the radar. If the car is detected, return YES, otherwise NO.(You can consider that the car is a line segment of length 1 and goes straight from x = 0 to the right)

Notice

- The number of radars is n, n <= 1000
- The radar’s coordinate x is a non-negative integer, y is an integer, and r is a positive integer.

Example

Given coordinates = [[0,2]], radius = [1], return "NO". Explanation: There is a radar at (0,2) that can detect a circle with a radius of 1 centered on (0,2) and the car will not be detected.

Given coordinates = [[0,2],[1,2]], radius = [1,2], return "YES" Explanation: There is a radar at (0,2) that can detect a circular area with a radius of 2 with a center of (0,2). Radars at (1,2) can detect (1,2) as Center, circular area with 2 radius. The No. 2 radar can detect the passing of the car.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## Blog link: https://code.dennyzhang.com/radar-detection ## Basic Ideas: only check the height ## Complexity: Time O(n), Space O(1) """ Definition for a point. class Point: def __init__(self, a=0, b=0): self.x = a self.y = b """ class Solution: """ @param coordinates: The radars' coordinate @param radius: Detection radius of radars @return: The car was detected or not """ def radarDetection(self, coordinates, radius): for i in range(len(coordinates)): y = coordinates[i].y r = radius[i] start, end = y-r, y+r if start<=0 and end>=1: return "YES" return "NO"

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