根據百分比選擇值

Question

我需要根據選擇該值的百分比幾率來選擇一個值。 例如：

• 10％的時間增量值a
• 20％的時間增量值b
• 30％的時間增量值c
• 40％的時間增量值d

百分比總是合計100％

我也遇到了幾個解決方案，如這一個 ，但已經確定，他們不可能是正確的。 這是使用上述解決方案構建的示例程序：

import java.util.Random;

public class Main {

    private static Random r = new Random();

    public static void main(String[] args) {
        final int iterations = 1000000;
        System.out.println("Testing percentage based random, " + iterations + " iterations");
        int onePercent = 0;
        int sixPercent = 0;
        int sevenPercent = 0;
        int thirtySixPercent = 0;
        int fiftyPercent = 0;
        // Those values add up to 100% overall
        for (int i = 0; i < iterations; i++) {
            int random = r.nextInt(100);
            if (random < 1) {
                onePercent++;
                continue;
            }
            if (random < 6) {
                sixPercent++;
                continue;
            }
            if (random < 7) {
                sevenPercent++;
                continue;
            }
            if (random < 36) {
                thirtySixPercent++;
                continue;
            }
            if (random < 50) {
                fiftyPercent++;
                continue;
            }
            // That can't be right because if random > 50 then nothing at all happens
        }
        System.out.println("One percent happened about " + (onePercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Six percent happened about " + (sixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Seven percent happened about " + (sevenPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Thirty six percent happened about " + (thirtySixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Fifty percent happened about " + (fiftyPercent / Float.valueOf(iterations)) * 100 + "% of the time");
    }
}

輸出：

Testing percentage based random, 1000000 iterations
One percent happened about 0.99649996% of the time
Six percent happened about 4.9925% of the time
Seven percent happened about 1.0029999% of the time
Thirty six percent happened about 29.001299% of the time
Fifty percent happened about 14.0191% of the time

預期產量：

Testing percentage based random, 1000000 iterations
One percent happened about 0.99649996% of the time
Six percent happened about 6.9925% of the time
Seven percent happened about 7.0029999% of the time
Thirty six percent happened about 36.001299% of the time
Fifty percent happened about 50.0191% of the time

我相信我需要使用某種算法將百分比轉換為從0到99的比例，以便隨機數生成器可以准確選擇一個值。 不過，我無法考慮如何做到這一點。

Answer 1

你的結果是正確的：

50％的事件發生在大約14.0191％的時間

50 - 36 = 14

百分之三十六的發生在29.001299％的時間

36 - 7 = 29

大約1.00％的時間發生了7％

7 - 6 = 1

....

如果您要總結所有“繼續”語句。

Answer 2

弄清楚了。 您需要跟蹤到目前為止測試的百分比並將其添加到當前測試中。

import java.util.Random;

public class Main {

    private static Random r = new Random();

    public static void main(String[] args) {
        final int iterations = 1000000;
        System.out.println("Testing percentage based random, " + iterations + " iterations");
        int onePercent = 0;
        int sixPercent = 0;
        int sevenPercent = 0;
        int thirtySixPercent = 0;
        int fiftyPercent = 0;
        // Those values add up to 100% overall
        for (int i = 0; i < iterations; i++) {
            int random = r.nextInt(100);
            int totalPercent = 0;
            if (random < totalPercent + 1) {
                onePercent++;
                continue;
            }
            totalPercent += 1;
            if (random < totalPercent + 6) {
                sixPercent++;
                continue;
            }
            totalPercent += 6;
            if (random < totalPercent + 7) {
                sevenPercent++;
                continue;
            }
            totalPercent += 7;
            if (random < totalPercent + 36) {
                thirtySixPercent++;
                continue;
            }
            totalPercent += 36;
            if (random < totalPercent + 50) {
                fiftyPercent++;
                continue;
            }
            totalPercent += 50;
            // That can't be right because if random > 50 then nothing at all happens
        }
        System.out.println("One percent happened about " + (onePercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Six percent happened about " + (sixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Seven percent happened about " + (sevenPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Thirty six percent happened about " + (thirtySixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Fifty percent happened about " + (fiftyPercent / Float.valueOf(iterations)) * 100 + "% of the time");
    }
}