计数排序

/**
 * 排序算法之计数排序
**/
#include <iostream>
#include <vector>
using namespace std;

void CountSort(vector<int> &arr, int maxVal) {
    int len = arr.size();
    if (len < 1)
        return;
    vector<int> count(maxVal+1, 0);
    vector<int> tmp(arr);
    for (auto x : arr)
        count[x]++;
    for (int i = 1; i <= maxVal; ++i)
        count[i] += count[i - 1];
    for (int i = len - 1; i >= 0; --i) {
        arr[count[tmp[i]] - 1] = tmp[i];
        count[tmp[i]]--;                //注意这里要减1
    }
}

int main()
{
    vector<int> arr = { 1,5,3,7,6,2,8,12,4,3,3 };
    int maxVal = 12;
    CountSort(arr,maxVal);
    for (auto x : arr)
        cout << x << " ";
    cout << endl;
    return 0;
}