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<C #> Find the maximum number of duplicates in the array,

Given an int array, there are repeated values. How can we find the maximum number of duplicates?

This is a question raised by someone in a community. The solution I think of is grouping.

1. group all elements in the array first. Then, repeated values will certainly be placed in a group;

2. Sort groups by the number of elements in the group;

3. The group with the largest number of elements has the largest number of duplicates.

 

Based on the above ideas, you can write the following code:

// Example array, 90 repeats 4 times, 1 repeats 2 times, 3 repeats 3 times int [] arr = {1, 1, 3, 3, 3, 7, 50, 15, 15, 90, 90, 90, 90,105};/** groups elements of the array first, * sort the number of elements in each group in descending order */var res = from n in arr group n by n into g orderby g. count () descending select g; // The first group in the group is the var gr = res. first (); foreach (int x in gr) {Console. write ("{0}", x );}

In the example array, 1 appears twice, 3 appears three times, 15 appears twice, and 90 appears four times. Obviously, the maximum number of repetitions is 90.
Use the Linq statement to group all elements in the source array according to the elements themselves. Then, use the Count method to calculate the number of elements in each group and sort them in descending order. In the first group in the result, the elements in the group are naturally the most repeated.

Therefore, the output result is:

Due to my limited personal character value, I can only come up with this simple method to deal with it. audience members, if you have a simpler method, be sure to post it and don't say "Jin Wu Zang Jiao ".

<C: if test = ""> how to judge

We recommend that you check the EL expression usage. The comparative expression should be written in {}.
<C: if test = "$ {limit = '1'}"> <! -- How should test be written here ?????? -->
<Input type = "button" value = "permission 1"/>
</C: if>
The EL expression can use = to compare two strings.

A simple program of C language Bubble Sorting

Main ()
{
Int I, j, temp;
Int a [10];
For (I = 0; I <10; I ++)
Scanf ("% d,", & a [I]);
For (j = 0; j <= 9; j ++)
{For (I = 0; I <10-j; I ++)
If (a [I]> a [I + 1])
{Temp = a [I];
A [I] = a [I + 1];
A [I + 1] = temp ;}
}
For (I = 1; I <11; I ++)
Printf ("% 5d,", a [I]);
Printf ("\ n ");
}

--------------
Bubble Algorithm
Algorithm Analysis and Improvement of Bubble Sorting
The basic idea of exchanging sorting is to compare the keywords of the records to be sorted in pairs. If the order of the two records is the opposite, the two records are exchanged until there is no reverse order record.
The basic concepts of application exchange sorting include Bubble sorting and quick sorting.

Bubble Sorting

1. Sorting Method
Vertically arrange the sorted record array R [1. n]. Each record R is considered as a bubble with the weight of R. key. According to the principle that a Light Bubble cannot be under a heavy bubble, scan the array R from the bottom up: Any Light Bubble scanned to a violation of this principle will make it "float" up ". This is repeated until the last two bubbles are light and heavy.
(1) initial
R [1. n] is an unordered area.

(2) First scan
The weights of two adjacent bubbles are compared from the bottom of the unordered area to the top. If the light bubbles are found to be in the lower and severe bubbles, the positions of the two bubbles are exchanged. That is, compare (R [n], R [n-1]), (R [n-1], R [N-2]),…, (R [2], R [1]); for each pair of bubbles (R [j + 1], R [j]), if R [j + 1]. key <R [j]. key, then the contents of R [j + 1] and R [j] are exchanged.
When the first scan is complete, the "lightest" bubble floated to the top of the interval, that is, the record with the smallest keyword is placed on the highest position R [1.

(3) second scan
Scan R [2. n]. When scanning is completed, the "light" bubble floated to the R [2] position ......
Finally, the sequential area R [1. n] can be obtained through n-1 scanning.
Note:
During the I-trip scan, R [1 .. I-1] and R [I.. n] are the current sequential and disordered areas, respectively. The scan continues from the bottom of the unordered area to the top of the area. When scanning is completed, the shortest bubbles in the area float to the top position R. The result is that R [1. I] is changed to a new ordered area.

2. Bubble sorting process example
Bubble Sorting of files whose keyword sequence is 49 38 65 97 76 13 27 49

3. Sorting Algorithm
(1) Analysis
Because each sort adds a bubble to the ordered area, there are n-1 bubbles in the ordered area after N-1 sort, in the disordered area, the bubble weight is always greater than or equal to the bubble weight in the ordered area. Therefore, the entire Bubble sorting process requires at most n-1 sorting.
If no bubble position exchange is found in a sorting, it means that all bubbles in the unordered area to be sorted meet the principle of being light and heavy. Therefore, the Bubble sorting process can be terminated after this sorting. Therefore, in the following algorithm, a Boolean exchange is introduced, which is set to FALSE before each sort starts. If an exchange occurs during the sorting process, set it to TRUE. Check exchange at the end of sorting. If exchange has not occurred, terminate the algorithm and no longer perform the next sorting.

(2) specific algorithms
Void BubbleSort (SeqList R)
{// R (l. n) is the file to be sorted. It uses bottom-up scanning to perform Bubble Sorting on R.
Int I, j;
Boolean exchange; // exchange flag
For (I = 1; I <G id = "1">