C Program to Find kth Smallest Element in Array using Partitioning

This is a C Program to find kth smallest element by method of partitioning. The same partitioning function which is used for Quicksort algorithm can be used.

Here is source code of the C Program to Find kth Smallest Element by the Method of Partitioning the Array. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
#include<stdio.h>
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```
#include<math.h>
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```
#include<time.h>
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```
#include<stdlib.h>
```
```
 
```
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int N = 20;
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int A[20];
```
```
 
```
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void swap(int dex1, int dex2) {
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```
    int temp = A[dex1];
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    A[dex1] = A[dex2];
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    A[dex2] = temp;
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}
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```
 
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int partition(int start, int end) {
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    int i = start + 1;
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    int j = i;
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    int pivot = start;
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    for (; i < end; i++) {
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        if (A[i] < A[pivot]) {
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            swap(i, j);
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            j++;
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        }
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    }
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    if (j <= end)
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        swap(pivot, (j - 1));
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    return j - 1;
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}
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```
 
```

void quick_sort(int start, int end, int K) {

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    int part;
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    if (start < end) {
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        part = partition(start, end);
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        if (part == K - 1)
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            printf("kth smallest element : %d ", A[part]);

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        if (part > K - 1)
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            quick_sort(start, part, K);
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        else
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            quick_sort(part + 1, end, K);

```
    }
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    return;
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}
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```
 
```
```
int main(int argc, char **argv) {
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    int i;
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    time_t seconds;
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    time(&seconds);
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    srand((unsigned int) seconds);
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```
 
```
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    for (i = 0; i < N; i++)
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        A[i] = rand() % (1000 - 1 + 1) + 1;

```
 
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    printf("The original sequence is:  ");

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    for (i = 0; i < N; i++)
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        printf("%d ", A[i]);
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    printf("\nEnter the Kth smallest you want to find: ");

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    int k;
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    scanf("%d", &k);
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    quick_sort(0, N, k);
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}
```

Output:

$ gcc KthSmallestUsingPartitioning.c
$ ./a.out
 
The original sequence is:  909 967 552 524 735 383 616 718 904 945 730 173 143 954 482 307 228 35 224 703 
Enter the Kth smallest you want to find: 3
kth smallest element : 173

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