Java Basic Learning Summary Five (recursive algorithm, bubble sort)

One: Recursive algorithm

Concept: Call your own method

The sample code is as follows:

1 @Test2     /**3 * Recursive summation4 * 5+4+3+2+1=155      */6      Public voidgetsum () {7         Longsum = SUM (5);8System.out.println ("sum=" +sum);9     }Ten  One      Public Static LongSuminti) { A         if(1 = =i) { -             return1; -}Else { the             returni + SUM (i-1); -         } -}

Explain:

When I=5, return to 5+sum (4),

When i=4, return to 4+sum (3),

When I=3, return to 3+sum (2),

When i=2, return to 2+sum (1),

When I=1, returns 1

Finally, the 5+4+3+2+1=15 is obtained;

Two: Bubble sort

Concept: If there are several numbers, 12, 23, 4, 3, 14

First: Take 12 compared with other numbers, if 12 is smaller than the other number, then swap position, which is descending order.

Original order: 12, 23, 4, 3, 14

After the first comparison: 23,12,4,3,14

Get a maximum value, on the leftmost side, in the second and subsequent numbers to compare, the same way as before

23,14,4,3,12

23,14,12,3,4

23,14,12,4,3

The sample code is as follows:

1 @Test2     /**3 * Bubble Sort4      */5      Public voidPupplesort () {6         int[] arr = {12, 23, 4, 3, 14 };7          for(inti = 0; i < arr.length; i++) {8              for(intj = i + 1; J < Arr.length; J + +) {9                 if(Arr[i] <Arr[j]) {Ten                     intTMP =Arr[i]; OneArr[i] =Arr[j]; AARR[J] =tmp; -                 } -             } the         } - System.out.println (arrays.tostring (arr)); -}

Java Basic Learning Summary Five (recursive algorithm, bubble sort)