整数排序的几种方法

网上看到有一位大神总结的代码，先记录如下：
````
class Solution {
public:
/*
* @param A: an integer array
* @return:
*/
void sortIntegers(vector

private:
// Quick sort
int partition(vector

    int pivot = a[(left + right) / 2];  
    while (left <= right) {  
        // find the date at left side shift to right side  
        while (left<=right && a[left]<pivot)  
            left++;  
        // find the data at right side shift to left side  
        while (left<=right && a[right]>pivot)  
            right--;  

        // swap  
        if (left <= right) {  
            swap(a, left, right);  
            left++;  
            right--;  
        }  
    }  
    return left;  
}  

void Qsort(vector<int> &a, int left, int right) {  
    if (left<0 || right<=0 || left>=right)  
        return;  

    int index = partition(a, left, right);  
    if (left < index-1)  
        Qsort(a, left, index-1);  
    if (index < right)  
        Qsort(a, index, right);  
}  

void quickSort(vector<int> &a) {  
    if (a.size() <= 1)  
        return;  
    Qsort(a, 0, a.size() - 1);  
}  

// Insertion Sort  
void insertionSort(vector<int> &a) {  
    for (int which=1; which < a.size(); which++) {  
        int val = a[which];  
        for (int i = 0; i < which; i++) {  
            if (a[i] > val) {  
                // do shift to   
                for (int j=which; j>i; j--) {  
                    a[j] = a[j-1];  
                }  
                a[i] = val;  
                break;  
            }  
        }  
    }  
}  

// Selection sort  
void swap(vector<int> &a, int index1, int index2) {  
    if (index1 == index2)  
        return;  
    auto it = a.begin();  
    int temp = *(it + index1);  
    *(it + index1) = *(it + index2);  
    *(it + index2) = temp;          
}  

int findSmallest(vector<int> &a, int start, int end) {  
    int min = start;  
    for (int i = start + 1; i <= end; i++) {  
        if (a[i] < a[min])  
            min = i;  
    }  

    return min;  
}  

void selectionSort1(vector<int> &a, int start, int end) {  
    if (start < end - 1) {  
        swap(a, start, findSmallest(a, start, end));  
        selectionSort1(a, start + 1, end);  
    }  
}  

void selectionSort1(vector<int> &a) {  
    if (a.size() <= 1)  
        return;  

    selectionSort1(a, 0, a.size() - 1);  
}  

// Selection sort  
void selectionSort(vector<int> &a) {  
    if (a.size() <= 1)  
        return;  

    for (int i = 0; i < a.size() - 1; i++) {  
        int min = i;  
        for (int j = i+1; j < a.size(); j++) {  
            if (a[j] < a[min])  
                min = j;  
        }  

        if (min != i) {  
            auto it = a.begin();  
            int temp = *(it + min);  
            *(it + min) = *(it + i);  
            *(it + i) = temp;                  
        }  
    }  
}  

// buble sort  
void bubleSort(vector<int> &a) {  
    if (a.size() <=1)  
        return;  

    for (int i = 0; i < a.size(); i++) {  
        for (int j = 1; j < a.size() - i; j++) {  
            if (a[j] < a[j - 1]) {  
                auto it = a.begin();  
                int temp = *(it + j);  
                *(it + j) = *(it + j - 1);  
                *(it + j - 1) = temp;  
            }  
        }  
    }      
}  

};
```