Counting sort

最新推荐文章于 2024-05-14 11:46:26 发布

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本文介绍了一种线性时间复杂度的排序算法——计数排序。该算法通过统计每个元素出现的次数来完成排序，适用于一定范围内的整数排序。文章详细展示了计数排序的实现过程，并提供了完整的Java代码。

The running time of counting sort is O(n), and usually, the running time of sorting algorithms will be either O(n^2) or O(n lgn), the reason why counting sort is O(n) is that it doesn't have the comparison.

public static int[] CountingSort(int[] input) {
    int max = input[0];
    int min = input[0];
    for (int i = 1; i < input.length; i++) {
        if (input[i] > max) max = input[i];
        if (input[i] < min) min = input[i];
    }
    int[] range = new int[max - min + 1];
    int[] tmpArray = new int[input.length];
    for (int i = 0; i < input.length; i++) {
    	range[input[i] - min] += 1;
    }
    for (int i = 1; i < range.length; i++) {
    	range[i] += range[i - 1];
    }
    for (int i = 0; i <  input.length; i++) {
    	tmpArray[range[input[i] - min] - 1] = input[i];
    	range[input[i] - min]--;
    }
    for (int i = 0; i < input.length; i++) {
        input[i] = tmpArray[i];
    }
    return range;
}