Leetcode:Sort colors 计数排序

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, 
white and blue.

Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively.

class Solution {
public:
    void sortColors(int A[], int n) {
        assert(A != NULL && n >= 0);
        auto result = minmax_element(A, A + n);
        int minVal = *result.first;
        int maxVal = *result.second;
        int totalCount = maxVal - minVal + 1;  
        if (totalCount == 1) return;
        int* count = new int[totalCount]();
        
        for (int i = 0; i < n; ++i) {
            ++(count[A[i] - minVal]);
        }
        
        for (int i = 1; i < totalCount; ++i) {
            count[i] += count[i-1];
        }
        
        int* tmp = new int[n]();
        for (int i = n - 1; i >= 0; --i) {   // 必须从后往前，否则不是稳定的算法
            tmp[count[A[i] - minVal] - 1] = A[i];
            --(count[A[i] - minVal]);
        }
        
        copy(tmp, tmp + n, A);
        
        delete[] count;
        delete[] tmp;
    }
};