Enter two integers, n and m, from the numbers 1, 2, 3 ,...... Random Number in n to make it equal

Question 21: programming, input two integers n and m, from Series 1, 2, 3 ,...... N is random, so that the sum is equal to m. All possible combinations are required. It is actually a backpack problem. Solution: 1. First, determine that if nm is used, the number of n greater than m cannot be involved in the combination, and then set it to nm; 2. Add the maximum number n to the nm,

Question 21: programming, input two integers n and m, from Series 1, 2, 3 ,...... N is random, so that the sum is equal to m. All possible combinations are required. It is actually a backpack problem. Solution: 1. first, it is judged that, if the nm is used, the number of n greater than m cannot be involved in the combination, and n = m; 2. add the maximum number n and n = m,

Question 21: programming, input two integers n and m, from Series 1, 2, 3 ,...... N is random, so that the sum is equal to m. All possible combinations are required. It is actually a backpack problem.

Solution:

1. First, it is judged that if n> m, the number of n greater than m cannot be involved in the combination, and n = m is set at this time;

2. If the maximum number n is added and n = m, the condition is met and the result is output;

3. solve n in two cases: (1) n is not added, n = n-1; m = m; recursion; (2) n is added, take n = n-1l, m = m-n, and Recursion

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1. Public class s21 {
2. Private static upload list List = new external list ();
3. /**
4. * Solution:
5. * 1. First, it is judged that if n> m, the number of n greater than m cannot be involved in the combination, and n = m is set at this time;
6. * 2. If the maximum number n is added and n = m, the condition is met and the output is successful;
7. * 3. Solve n in two cases: n is not added, n = n-1, m = m, and recursion;
8. * 4. Add n, n = n-1, m = m-n, and recursion.
9. * 5. End.
10. * @ Param sum
11. * @ Param n
12. */
13. Public static void findSum (int sum, int n)
14. {
15. If (n <1 | sum <1)
16. Return;
17. If (sum> n)
18. {
19. List. add (n );
20. FindSum (sum-n, n-1); // Add n, n = n-1, m = m-n
21. List. pop ();
22. FindSum (sum, n-1); // n is not added, n = n-1, m = m
23. }
24. Else
25. {
26. System. out. print (sum); // sum <n, directly output n to meet
27. For (int I = 0; I <list. size (); I ++)
28. System. out. print ("" + list. get (I ));
29. System. out. println ();
30. }
31. }
32. /**
33. * @ Param args
34. */
35. Public static void main (String [] args ){
36. // TODO Auto-generated method stub
37. Int sum = 10;
38. Int n = 6;
39. FindSum (sum, n );
40. }
41. }