Pat Advanced 1089. Insert or Merge (25), 同Basic 1035. 插入与归并(25)

注意点：

这里的归并排序（Merge Sort），需要按照题意要求去归并。

题意：

归并排序进行如下迭代操作：先将原始序列看成N个只包含1个元素的有序子序列，

然后每次迭代归并两个相邻的有序子序列，

直到最后只剩下1个有序的序列。

Merge
sort works as follows: Divide the unsorted list into N sublists,

each containing 1 element (a list of 1 element is considered sorted).

Then repeatedly merge two adjacent sublists to produce new sorted sublists

until there is only 1 sublist remaining.

思路：

方法一：直观的解法，分别写出 Insert Sort 和Merge Sort，然后比较每一次迭代后的顺序，判断并输出；

方法二：理解插入和归并排序，利用标准模版库中的 Sort 函数，有序地一轮一轮 Sort 数组，来模拟插入和归并每轮的输出。

方法一：Java代码

import java.util.Scanner;

public class Main{
static int arrLen;
static int[] unSorted4Insert = new int[101];
static int[] unSorted4Merge = new int[101];
static int[] temp = new int[101];
static String lineToJudge;
static boolean onceMoreFlag=false;
static boolean isMerge =false;
static boolean isInsert=false;

//	{3,1,2,8}
public static void insertSort02(){
for(int i=1;i<arrLen;i++){
if(unSorted4Insert[i]<unSorted4Insert[i-1]){
int temp =unSorted4Insert[i];
int j=i-1;
while(j>=0 && unSorted4Insert[j]>temp){
unSorted4Insert[j+1]=unSorted4Insert[j];
j--;
}
unSorted4Insert[j+1]=temp;
}

if(onceMoreFlag){
break;
}
StringBuilder sb =new StringBuilder();
for(int f=0;f<arrLen;f++){
sb.append(unSorted4Insert[f]+" ");
}
if(sb.toString().trim().equals(lineToJudge)){
isInsert=true;
onceMoreFlag=true;
}
}
}

public static void merge02(int start01,int end01,int start02,int end02){
int start1 =start01;
int end1   =end01;
int start2 =start02;
int end2   =end02;
int i=start01;

while(start1<=end1 && start2<=end2){
if(unSorted4Merge[start1]<=unSorted4Merge[start2]){
temp[i]=unSorted4Merge[start1];
i++;
start1++;
}
else{
temp[i]=unSorted4Merge[start2];
i++;
start2++;
}
}
while(start1<=end1){
temp[i]=unSorted4Merge[start1];
i++;
start1++;
}
while(start2<=end2){
temp[i]=unSorted4Merge[start2];
i++;
start2++;
}

for(int f=start01;f<=end02;f++){
unSorted4Merge[f]=temp[f];
}

}

public static void mergeSort02(int start,int end){
for(int mergeStepLen=2   ;mergeStepLen/2<arrLen;mergeStepLen*=2){
for(int i=0 ;i<arrLen ;i+=mergeStepLen){
int start1=i;
int end1  =i+mergeStepLen/2-1;//下标和长度相差1

int start2=end1+1;
if(start2>=arrLen){break;}
int a=i+mergeStepLen-1;
int b=arrLen-1;
int end2  =a<b?a:b;
merge02(start1,end1,start2,end2);
}

if(onceMoreFlag){
break;
}
StringBuilder sb =new StringBuilder();
for(int f=0;f<arrLen;f++){
sb.append(unSorted4Merge[f]+" ");
}
if(sb.toString().trim().equals(lineToJudge)){
isMerge=true;
onceMoreFlag=true;
}

}
}

public static void main(String[] args) {
Scanner sc =new Scanner(System.in);
arrLen =sc.nextInt();
for(int i =0;i<arrLen;i++){
unSorted4Insert[i]=sc.nextInt();
unSorted4Merge[i]=unSorted4Insert[i];
}

StringBuilder sb =new StringBuilder();
for(int i =0;i<arrLen;i++){
sb.append(sc.nextInt()+" ");
}
lineToJudge = sb.toString().trim();

insertSort02();

if(isInsert){
System.out.println("Insertion Sort");

sb.setLength(0);
for(int f=0;f<arrLen;f++){
sb.append(unSorted4Insert[f]+" ");
}
System.out.print(sb.toString().trim());
}
else{
mergeSort02(0,arrLen-1);

System.out.println("Merge Sort");

sb.setLength(0);
for(int f=0;f<arrLen;f++){
sb.append(unSorted4Merge[f]+" ");
}
System.out.print(sb.toString().trim());
}

}
}

【参考博客】

【方法一】：直接写出Insert Sort 和 Merge Sort
http://www.cnblogs.com/GoFly/p/4297485.html
【方法二】：利用标准模版库提供的Sort 函数，模拟一轮一轮的Insert Sort 和 Merge Sort
http://blog.csdn.net/cstopcoder/article/details/42567287 http://tech.bingfengsa.com/a/20141201/39766.html