归并排序思想应用

package cn.edu.ujn.offersword;
public class C5_36_InversePairs {
/**
 * @date 2016-09-16
 * @number 03
 * @author SHQ
 */
public static void main(String[] args) {
int [] array = {1,2,3,4,5,6,7,0};
System.out.println(InversePairs(array));
}
    private static int InversePairs(int [] array) {
        if(array == null || array.length == 0)
        {
            return 0;
        }
        int len = array.length;
        int[] copy = new int[len];	// 设置一辅助数组，用于存放排序结果
        for(int i = 0; i < len; i++)
        {
            copy[i] = array[i];
        }
        int count = InversePairsCore(array, copy, 0, len-1);
        return count;
    }
    
    private static int InversePairsCore(int[] array, int[] copy,int low, int high)
    {
        if(low == high)
        {
            return 0;
        }
        int mid = (low + high) >> 1;//使用左移运算符 >>,运算速度高于除法运算符
        int leftCount = InversePairsCore(array, copy, low, mid) % 1000000007;
        int rightCount = InversePairsCore(array, copy, mid+1, high)% 1000000007;
        int count = 0;
        int i = mid;
        int j = high;
        int locCopy = high;
        while(i >= low && j > mid)
        {
            if(array[i] > array[j])
            {
                count += j - mid;
                copy[locCopy--] = array[i--];
                if(count >= 1000000007) // 数值过大求余
                {
                    count %= 1000000007;
                }
            }
            else
            {
                copy[locCopy--] = array[j--];
            }
        }
        for(; i >= low; i--)
        {
            copy[locCopy--] = array[i];
        }
        for(; j > mid; j--)
        {
            copy[locCopy--] = array[j];
        }
        for(int s = low; s <= high; s++)
        {
            array[s] = copy[s];
        }
        return (leftCount + rightCount + count) % 1000000007;
    }
}

package cn.edu.ujn.offersword;
 
import java.util.Arrays;
 
public class MergeSort {  
    /**
     * 归并排序
     * 简介:将两个（或两个以上）有序表合并成一个新的有序表 即把待排序序列分为若干个子序列，每个子序列是有序的。
     * 然后再把有序子序列合并为整体有序序列
     * 时间复杂度为O(nlogn)
     * 空间复杂度为O(n)
     * 稳定排序方式
     * @param nums 待排序数组
     * @return 输出有序数组
     */  
    public static int[] sort(int[] nums, int low, int high) {  
        int mid = (low + high) / 2;  
        if (low < high) {  
            // 左边  
            sort(nums, low, mid);  
            // 右边  
            sort(nums, mid + 1, high);  
            // 左右归并  
            merge(nums, low, mid, high);  
        }  
        return nums;  
    }  
  
    public static void merge(int[] nums, int low, int mid, int high) {  
        int[] temp = new int[high - low + 1];  
        int i = low;// 左指针  
        int j = mid + 1;// 右指针  
        int k = 0;
  
        // 把较小的数先移到新数组中  
        while (i <= mid && j <= high) {  
            if (nums[i] < nums[j]) {  
                temp[k++] = nums[i++];  
            } else {  
                temp[k++] = nums[j++];  
            }  
        }  
  
        // 把左边剩余的数移入数组  
        while (i <= mid) {  
            temp[k++] = nums[i++];  
        }  
  
        // 把右边边剩余的数移入数组  
        while (j <= high) {  
            temp[k++] = nums[j++];  
        }  
  
        // 把新数组中的数覆盖nums数组  
        for (int k2 = 0; k2 < temp.length; k2++) {  
            nums[k2 + low] = temp[k2];  
        }  
    }  
      
    // 归并排序的实现  
    public static void main(String[] args) {  
        int[] nums = { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };  
        MergeSort.sort(nums, 0, nums.length-1);  
        System.out.println(Arrays.toString(nums));
    }  
}

    	int len1 = 0;
    	int len2 = getLength(pHead2);
    	int difLen = 0;
    	// pHeadTmp1指向较长链表
    	ListNode pHeadLong = pHead1;
    	while(pHeadLong != null){
    	len1++;
    	pHeadLong = pHeadLong.next;
    	}
    	// pHeadTmp2指向较短链表
    	ListNode pHeadShort = pHead2;
    	if(len1 > len2){
    	difLen = len1 - len2;
    	}else{
// 此处会抛异常(在本地无异常)
    	pHeadLong = pHead2;
    	pHeadShort = pHead1;
    	difLen = len2 - len1;
    	}

    private static int getLength(ListNode pHead){
    	int len = 0;
    	while(pHead != null){
    	len++;
    	pHead = pHead.next;
    	}
    	return len;
    }