四舍五入到小数点后2位

Question

获取以下数字集-->

[5.1429,5.1429,5.1429,5.1429,5.1429,5.1429,5.1426]
[0.8333,0.8333,0.8333,0.8333,0.8333,0.8335]

当相加时，这些给出一个整数。

[5.14, 5.14, 5.14, 5.14, 5.14, 5.14, 5.14]
[0.83, 0.83, 0.83, 0.833, 0.83, 0.83]

Answer 1

如果通过递减第三个小数并向下四舍五入对输入进行排序，除了达到目标的足够数量之外，将引入最小的绝对四舍五入误差--同时保持总数不变。

举个简单的例子：

输入

0.132, 0.226, 0.257, 0.385 // sums up to 1.00

0.257, 0.226, 0.385, 0.132

0.25, 0.22, 0.38, 0.13 // sums up to 0.98

0.26, 0.23, 0.38, 0.13 // sums up to 1.00

public void printRounded(double[] ds) {
    // create wrapper objects
    int n = ds.length;
    Wrapper[] ws = new Wrapper[n];
    for (int i = 0; i < n; i++)
        ws[i] = new Wrapper(i, (int)(ds[i] * 1000) % 10, (int)(ds[i] * 100));

    // sort by third decimal, descending
    Arrays.sort(ws, new Comparator<Wrapper>() {
        public int compare(Wrapper o1, Wrapper o2) {
            return o2.thirdDecimal.compareTo(o1.thirdDecimal);
        }
    });

    // find number of elements that must be rounded up and increment
    int sum = 0;
    for (int i = 0; i < n; i++)
        sum += ws[i].prefix;
    int numberToIncrement = 100 - (sum % 100);
    for (int i = 0; i < numberToIncrement ; i++)
        ws[i].prefix++;

    // sort back to input order
    Arrays.sort(ws, new Comparator<Wrapper>() {
        public int compare(Wrapper o1, Wrapper o2) {
            return o1.index.compareTo(o2.index);
        }
    });

    // print values
    for (int i = 0; i < n; i++) {
        System.out.println(ws[i].prefix / 100 + "." ws[i].prefix % 100);
    }
}

private class Wrapper {
    public Wrapper(int index, int thirdDecimal, int prefix) {
        this.index = index;
        this.thirdDecimal = thirdDecimal;
        this.prefix = prefix;
    }

    public int index;
    public int thirdDecimal;
    public int prefix;
}

当然，您可以将ints转换回double并使用标准格式，而不是使用自定义格式。