464.Sort Integers II-整数排序 II（容易题）

整数排序 II

1. 题目

   给一组整数，按照升序排序。使用归并排序，快速排序，堆排序或者任何其他 O(n log n) 的排序算法。

2. 样例

   给出 [3, 2, 1, 4, 5], 排序后的结果为 [1, 2, 3, 4, 5]。

3. 题解

1.快速排序

public class Solution {    /**     * @param A an integer array     * @return void     */    public void sortIntegers2(int[] A) {        quickSort(A, 0, A.length - 1);    }    private void quickSort(int[] a, int left, int right)    {        if (left < right)        {            int temp = a[left];            int i = left;            int j = right;            while (i < j)            {                while (j >i && a[j] >= temp)                {                    j--;                }                while (i < j && a[i] <= temp)                {                    i++;                }                if (i < j)                {                    swap(a, i, j);                }            }            swap(a, left, j);            quickSort(a,left,i-1);            quickSort(a, i+1, right);        }    }}

2.归并排序

public class Solution {    /**     * @param A an integer array     * @return void     */    public void sortIntegers2(int[] A) {        mergeSort(A, 0, A.length - 1);    }    private void mergeSort(int[] a, int low, int hi)    {        if (low < hi)        {            int mid = (low + hi) / 2;            mergeSort(a, low, mid);            mergeSort(a, mid + 1, hi);            mergeArray(a, low, mid, hi);        }    }    private void mergeArray(int[] a, int low, int mid, int hi)    {        if (low > mid)        {            return;        }        int[] temp = new int[hi - low + 1];        int i = low;        int j = mid + 1;        int k = 0;        while (i <= mid && j <= hi)        {            temp[k++] = a[i] < a[j] ? a[i++] : a[j++];        }        while (i <= mid)        {            temp[k++] = a[i++];        }        while (j <= hi)        {            temp[k++] = a[j++];        }        for (int k2 = 0; k2 < temp.length; k2++)        {            a[low + k2] = temp[k2];        }    }}

3.堆排序

public class Solution {    /**     * @param A an integer array     * @return void     */    public void sortIntegers2(int[] A) {        heapSort(A,A.length);    }    private void heapSort(int[] a, int n)    {        //建立最大堆        for (int i = n/2 - 1;i >= 0;i--)        {            minHeapAdjust(a, i, n);        }        //排序        for (int i = n - 1; i >= 1; i--)        {            swap(a, i, 0);            minHeapAdjust(a, 0, i);        }    }    private void minHeapAdjust(int[] a, int i, int n)    {        int j,tmp;        tmp = a[i];        j = 2 * i + 1;        while (j < n)        {            if (j + 1 < n && a[j+1] > a[j])            {                j++;            }            if (a[j] < tmp)            {                break;            }            a[i] = a[j];            i = j;            j = 2 * i + 1;        }        a[i] = tmp;    }    private void swap(int[] a, int i, int j)    {        int temp = a[j];        a[j] = a[i];        a[i] = temp;    }

Last Update 2016.9.18