Two-way merge sort (also called merge sort)

The following figure shows the two-way merge process.

The core code of the two-way merge is the merge () function

It merges 2 segmented arrays together in an orderly fashion.

In Array A,

From P to Q is an array, from Q to R is another array

So how do you combine the 2 arrays together in order to group A new array a?

Steps:

First step: Open an array of L, storing the elements of P to Q (that is, the left array that needs to be merged)

Part II: Open an array r, storing the elements of Q to R (that is, the right-hand array that needs to be merged)

The third step: The Last of the 2 arrays is also added an infinite number (can be expressed in 0x7fff), so the open array space is more than 1 characters of space

Fourth step: L and R numbers are compared one by one, the smaller first placed in the array a (starting from the array a "0" to store, and then overwrite the original number), and then the smaller array pointer moves backwards, pointing to the next one and another array comparison

[CPP]View PlainCopy

2. The first parameter is the array that needs to be sorted, and the 2nd parameter is the first array of the split start element subscript
4. The 3rd parameter is the subscript of the last 1 elements of the first array of the split
6. The 4th parameter is the subscript for the last 1 elements of an array
8. void Merge (int *a,int p,int q,int r)
10. {
12. int n1,n2,i,j,k,g;
14. n1=q-p+1;
16. N2=r-q;
18. int *l,*r;
20. l= (int *) malloc (sizeof (int) * (n1+1));
22. r= (int *) malloc (sizeof (int) * (n2+1));
24. L[N1]=0X7FFF; //Open the left and right 2 arrays the last 1 numbers are set to the maximum value
26. R[N2]=0X7FFF;
28. g=0;
30. For (i=p;i<=q;i++)
32. {
34. L[g]=a[i];
36. g++;
38. }
40. g=0;
42. For (i=q+1;i<=r;i++)
44. {
46. R[g]=a[i];
48. g++;
50. }
52. //Compare the left and right arrays, and write the smaller values to the original array
54. j=k=0;
56. For (i=p;i<=r;i++)
58. {
60. if (l[j]<r[k])
62. {
64. A[I]=L[J];
66. j + +;
68. }
70. Else
72. {
74. A[I]=R[K];
76. k++;
78. }
80. }
82. }

Full code:

[CPP]View PlainCopy

2. #include <iostream>
4. Using namespace std;
8. The first parameter is the array that needs to be sorted, and the 2nd parameter is the first array of the split start element subscript
10. The 3rd parameter is the subscript of the last 1 elements of the first array of the split
12. The 4th parameter is the subscript for the last 1 elements of an array
14. void Merge (int *a,int p,int q,int r)
16. {
18. int n1,n2,i,j,k,g;
20. n1=q-p+1;
22. N2=r-q;
24. int *l,*r;
26. l= (int *) malloc (sizeof (int) * (n1+1));
28. r= (int *) malloc (sizeof (int) * (n2+1));
30. L[N1]=0X7FFF; //Open the left and right 2 arrays the last 1 numbers are set to the maximum value
32. R[N2]=0X7FFF;
34. g=0;
36. For (i=p;i<=q;i++)
38. {
40. L[g]=a[i];
42. g++;
44. }
46. g=0;
48. For (i=q+1;i<=r;i++)
50. {
52. R[g]=a[i];
54. g++;
56. }
58. //Compare the left and right arrays, and write the smaller values to the original array
60. j=k=0;
62. For (i=p;i<=r;i++)
64. {
66. if (l[j]<r[k])
68. {
70. A[I]=L[J];
72. j + +;
74. }
76. Else
78. {
80. A[I]=R[K];
82. k++;
84. }
86. }
88. }
92. void MergeSort (int *a,int p,int r)
94. {
96. int q;
98. if (p<r) //When the first element is less than the last 1 elements, continue to perform recursion until only one element is left (parameter p=r)
100. {
102. q= (P+R)/2;
104. MergeSort (A,P,Q);
106. MergeSort (A,Q+1,R);
108. Merge (A,P,Q,R);
110. }
112. }
116. void Main ()
118. {
120. int a[5]={5,3,4,23,11};
122. MergeSort (a,0,4);
124. For (int i=0;i<5;i++)
126. cout<<a[i]<<endl;
128. System ("pause");
130. }

Two-way merge sort (also called merge sort)