算法-排序-计数排序（包含对非负数和整数的排序）

计数排序

时间复杂度O（n）
特点：稳定
限制：对0到maximum中的数进行排序
maximum要求，比数组中最大值大或者相等
有拓展版本的计数排序（在文章基数排序内）
基数排序链接

void counting_sort(int *input_array,int *out_array,int length,int maximum)
{int* count_array = new int [maximum+1];for (int i = 0; i < maximum + 1; ++i) {count_array[i] = 0;}for (int i = 0; i < length; ++i) {count_array[input_array[i]] = count_array[input_array[i]] + 1;}for (int i = 1; i < maximum + 1; ++i) {count_array[i] = count_array[i] + count_array[i-1];}for (int i = length - 1; i >=0 ; i--) {out_array[count_array[input_array[i]]-1] = input_array[i];count_array[input_array[i]] = count_array[input_array[i]] - 1;}delete [] count_array;
}

拓展版本1⃣️
带Key版本，缺点只能对Key为非负数排序

void counting_sort(vector<KeyValuePair>& array,int key_maximum)
{int *count_array = new int[key_maximum + 1];for (int i = 0; i < key_maximum+1; ++i) {count_array[i] = 0;}for (int i = 0; i < array.size(); ++i) {count_array[array[i].key] = count_array[array[i].key]+1;}for (int i = 1; i < key_maximum+1; ++i) {count_array[i] = count_array[i] + count_array[i-1];}vector<KeyValuePair> temp_array(array.size());for (int i = array.size()-1; i >=0 ; --i) {temp_array[count_array[array[i].key]-1] = array[i];count_array[array[i].key] = count_array[array[i].key] - 1;}for (int i = 0; i < array.size(); ++i) {array[i] = temp_array[i];}delete [] count_array;
}

2⃣️优化版本，对任意正整数排序

void counting_sort_by_key(vector<KeyValuePair>& array,int key_minimum = - 9,int key_maximum = 9);

void counting_sort_by_key(vector<KeyValuePair>& array,int key_minimum,int key_maximum)
{int inverter_count = key_maximum - key_minimum + 1;int *count_array = new int[inverter_count];for (int i = 0; i < inverter_count; ++i) {count_array[i] = 0;}for (int i = 0; i < array.size(); ++i) {count_array[array[i].key - key_minimum] = count_array[array[i].key - key_minimum] + 1;}for (int i = 1; i < inverter_count; ++i) {count_array[i] = count_array[i] + count_array[i-1];}vector<KeyValuePair> temp_array(array.size());for (int i = array.size() - 1; i >=0 ; --i) {temp_array[count_array[array[i].key - key_minimum]-1] = array[i];count_array[array[i].key - key_minimum] = count_array[array[i].key - key_minimum] - 1;}for (int i = 0; i < array.size(); ++i) {array[i] = temp_array[i];}delete [] count_array;
}