Given the radius and x-y positions of the center of a circle, write a function randPoint
which generates a uniform random point in the circle.
Note:
- input and output values are in floating-point.
- radius and x-y position of the center of the circle is passed into the class constructor.
- a point on the circumference of the circle is considered to be in the circle.
randPoint
returns a size 2 array containing x-position and y-position of the random point, in that order.
Example 1:
Input: ["Solution","randPoint","randPoint","randPoint"] [[1,0,0],[],[],[]] Output: [null,[-0.72939,-0.65505],[-0.78502,-0.28626],[-0.83119,-0.19803]]
Example 2:
Input: ["Solution","randPoint","randPoint","randPoint"] [[10,5,-7.5],[],[],[]] Output: [null,[11.52438,-8.33273],[2.46992,-16.21705],[11.13430,-12.42337]]
Explanation of Input Syntax:
The input is two lists: the subroutines called and their arguments. Solution
's constructor has three arguments, the radius, x-position of the center, and y-position of the center of the circle. randPoint
has no arguments. Arguments are always wrapped with a list, even if there aren't any.
A:
主要就是产生一个随机数:
C++ 中用 srand() 和 rand()
class Solution { public: Solution(double radius, double x_center, double y_center) { r = radius; x = x_center, y = y_center; srand(static_cast<unsigned int>(std::time(nullptr))); } vector<double> randPoint() { double tmpX = rand(); tmpX = (tmpX / RAND_MAX* 2 -1) *r; // in range [-1, 1]
double tmpY = rand(); tmpY = (tmpY / RAND_MAX* 2 -1) *r; // in range [-1, 1]
if(tmpX * tmpX + tmpY * tmpY <= r*r){ return vector<double>{x+tmpX,y+tmpY}; }else{ return randPoint(); } } private: double x, y; double r; }; /** * Your Solution object will be instantiated and called as such: * Solution* obj = new Solution(radius, x_center, y_center); * vector<double> param_1 = obj->randPoint(); */
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