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Code03_EqualProbabilityRandom.java
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67 lines (55 loc) · 1.37 KB
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package class02;
public class Code03_EqualProbabilityRandom {
// 内部内容不可见
public static int f() {
return Math.random() < 0.8 ? 0 : 1;
}
// 等概率返回0和1
public static int g() {
int first = 0;
do {
first = f(); // 0 1
} while (first == f());
return first;
}
// 这个结构是唯一的随机机制
// 你只能初始化并使用，不可修改
public static class RandomBox {
private final double p;
// 初始化时请一定满足：0 < zeroP < 1
public RandomBox(double zeroP) {
p = zeroP;
}
public int random() {
return Math.random() < p ? 0 : 1;
}
}
// 底层依赖一个以p概率返回0，以1-p概率返回1的随机函数rand01p
// 如何加工出等概率返回0和1的函数
public static int rand01(RandomBox randomBox) {
int num;
do {
num = randomBox.random();
} while (num == randomBox.random());
return num;
}
public static void main(String[] args) {
int[] count = new int[2];// 0 1
for (int i = 0; i < 1000000; i++) {
int ans = g();
count[ans]++;
}
System.out.println(count[0] + " , " + count[1]);
// double zeroP = 0.88;
// RandomBox randomBox = new RandomBox(zeroP);
//
// int testTime = 10000000;
// int count = 0;
// for (int i = 0; i < testTime; i++) {
// if (rand01(randomBox) == 0) {
// count++;
// }
// }
// System.out.println((double) count / (double) testTime);
}
}