Java-based Bubble Sorting

Java-based Bubble Sorting

Bubble Sorting:

It is to compare two adjacent elements by index. If the value is greater than/less than (depending on whether the order needs to be ascending or descending), it will be replaced. Otherwise, it will not be changed.

This round down, compared n-1 times, n is equal to the number of elements; N-2, n-3... until the last round, compared to 1

Therefore, the number of comparisons is decreasing from n-1 to 1.

The total number of comparisons is: 1 + 2 + 3 +... + (n-1), calculated using an equal deviation formula: (1 + N-1)/2 * (n-1) => n/2 * (n-1) => (n ^ 2-n) * 0.5

The time complexity of the algorithm is represented by large O: O (n ^ 2), ignoring the coefficients 0.5 and constant-n

Public class BubbleSort {public static void main (String [] args) {int len = 10; int [] ary = new int [len]; Random random = new Random (); for (int j = 0; j <len; j ++) {ary [j] = random. nextInt (1000);} System. out. println ("------- before sorting ------"); for (int j = 0; j <ary. length; j ++) {System. out. print (ary [j] + "");}/** in ascending order, Asc1 and Asc2 optimize the number of internal cycles, better * Total number of comparisons: * Asc1, Asc2 :( 1 + N-1)/2 * (n-1) => n/2 * (n-1) => n * (n-1) /2 => (n ^ 2-n)/2 * Asc: n ^ 2-n * // orderAsc (ary); // orderAsc2 (ary); orderAsc1 (ary ); // in descending order, you only need to replace the judgment size with} static void orderAsc (int [] ary) {int count = 0; // number of comparisons int len = ary. length; for (int j = 0; j <len; j ++) {// number of fixed outer loops for (int k = 0; k <len-1; k ++) {// Number of inner fixed loops if (ary [k]> ary [k + 1]) {ary [k] = ary [k + 1] + (ary [k + 1] = ary [k]) * 0; // One-Step swap/* swap two variable values * a = a + B * B = a-B * a = a-B */} count ++;} System. out. println ("\ n ----- after orderAsc Ascending Order ------ times:" + count); for (int j = 0; j <len; j ++) {System. out. print (ary [j] + "") ;}} static void orderAsc1 (int [] ary) {int count = 0; // number of comparisons int len = ary. length; for (int j = 0; j <len; j ++) {// number of fixed outer loops for (int k = len-1; k> j; k --) {// decrease the number of times the inner layer is compared from large to small if (ary [k] <ary [k-1]) {ary [k] = ary [k-1] + (ary [k-1] = ary [k]) * 0; // One-Step switching} count ++ ;}} system. out. println ("\ n ----- orderAsc1 in ascending order ------ times:" + count); for (int j = 0; j <len; j ++) {System. out. print (ary [j] + "") ;}} static void orderAsc2 (int [] ary) {int count = 0; // number of comparisons int len = ary. length; for (int j = len-1; j> 0; j --) {// number of fixed Outer Loops/** k <j; total number of comparisons = (n ^ 2-n)/2 */for (int k = 0; k <j; k ++) {// decrease the number of times the inner layer is compared from large to small if (ary [k]> ary [k + 1]) {ary [k] = ary [k + 1] + (ary [k + 1] = ary [k]) * 0; // One-Step switching} count ++ ;}} system. out. println ("\ n ----- orderAsc2 in ascending order ------ times:" + count); for (int j = 0; j <len; j ++) {System. out. print (ary [j] + "");}}}

Print

------- Before sorting ------ 898 7 862 286 879 660 433 724 316 ----- orderAsc1 after ascending sorting ------ times: 737 457 286 316 433 660 724 737 862 879 898