算法导论：第二章总结

 

 

SELECTION-SORT(A)



n : length[A]

	for j : 1 to n − 1

		do smallest : j

			for i : j + 1 to n

				do if A[i] < A[smallest] 

					then smallest : i

			exchange A[j] and A[smallest]

 

INSERTION-SORT（A）



for j : 2 to length[A]

	do key : A[j]

	i : j-1

	while i>0 and A[i]>key

		do A[i+1] : A[i]

			i : i-1

	A[i+1] : key

 

MERGE(A, p, q, r) 

n1 : q-p+1 

n2 : r-q 

create arrays L[1..n1+1] and R[1..n2+1]

for i : 1 to n1     

	do L[i] : A[p+i-1] 

for j : 1 to n2     

	do R[j] : A[q+j]

L[n1+1] :  ∞

L[n2+1] :  ∞

i : 1

j : 1

for k : p to r

	do if L[i]<=R[j]

		then A[k] : L[i]

			i : i+1

		else A[k] : R[j]

			j : j+1



MERGE-SORT(a, p, r)



if p<r

	then q : (p+r)/2

		MERGE-SORT(A, p , q)

		MERGE-SORT(A, q+1, r)

		MERGE(a, p, q, r)

  

BUBBLESORT(A)



for i : 1 to length[A]

    do for j : length[A] downto i+1

        do if A[j] < A[j-1]

            then exchange A[j] and A[j-1]

 

自己的插入排序：

 1 #include <stdio.h>

 2 #include <string.h>

 3 #define N 12

 4 

 5 int A[N] ={0,4,8,5,9,1,6,3};

 6 

 7 

 8 void insertion_sort(int A[]){

 9     int key,i,j;

10     for(j=2; j<8; ++j){

11         key = A[j];

12         i = j-1;

13         while(i>0 && A[i]>key){

14             A[i+1] = A[i];

15             i = i-1;

16         }

17         A[i+1] = key;

18     }

19 }

20 

21 int main(int argc, char const *argv[])

22 {

23     

24     insertion_sort(A);

25     for (int i = 0; i < 10; ++i)

26     {

27         printf("%d ", A[i]);

28     }

29     printf("\n");

30     return 0

 

 

自己写的合并排序：

 1 #include <stdio.h>  

 2 #include <iostream>  

 3 using namespace std; 

 4  

 5 void Merge(int* A,int p,int q,int r) 

 6 { 

 7     int n1= q-p+1; 

 8     int n2= r-q; 

 9      

10     int *L= new int[n1+1]; 

11     int *R= new int[n2+1]; 

12  

13     int i=0; 

14     int j=0; 

15  

16     for(i=0;i<n1;i++) 

17     { 

18         L[i]=A[p+i-1]; 

19          

20     } 

21      

22     for(j=0;j<n2;j++) 

23     { 

24         R[j]=A[q+j]; 

25      

26     } 

27     L[n1] = 100;

28     R[n2] = 100;

29      

30     i = 0; 

31     j = 0; 

32      

33     for(int k = p-1;k < r; k++) 

34     { 

35         if(L[i]<=R[j]) 

36         { 

37             A[k] = L[i]; 

38             i = i+1;    

39         } 

40         else 

41         { 

42             A[k] = R[j]; 

43             j = j+1;     

44         } 

45     } 

46 }  

47  

48 void Merge_Sort(int *A,int p,int r) 

49 { 

50     if(p<r) 

51     { 

52         int q=(p+r)/2; 

53         Merge_Sort(A,p,q); 

54         Merge_Sort(A,q+1,r); 

55         Merge(A,p,q,r); 

56     } 

57 } 

58  

59 int A[15] = {11,12,13,14,15,1,2,3,4,5,6,7,8,9,10};  

60  

61 int main(int argc, char **argv) 

62 { 

63     Merge_Sort(A,1,15); 

64      

65     for(int i=0;i<15;i++) 

66     { 

67         cout<<A[i]<<"\t"; 

68     } 

69     cout<<endl; 

70     return 0; 

71 }