fix lgtm error and add basic docs

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Krishna Vedala 2020-07-11 00:10:22 -04:00
parent d1dfde4f89
commit 47958fb003
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@ -1,46 +1,89 @@
/**
* @file union_find.c
* @brief [Union
* find](https://en.wikipedia.org/wiki/Disjoint-set_data_structure) algorithm.
*/
#include <stdio.h> #include <stdio.h>
#include <stdlib.h>
#define MAX_SIZE 1000 /**< maximum number of elements in the set */
int p[1000000]; /**
int find(int x) * @brief Find index of or value in an array
*
* @param [in,out] p array to search and update
* @param x value to search
* @return value at the index `x`
*/
int find(int *p, int x)
{ {
if (x >= MAX_SIZE)
{
fprintf(stderr, "Out-of bounds value\n");
exit(EXIT_FAILURE);
}
if (p[x] == x) if (p[x] == x)
{ {
return x; return x;
} }
else else
{ {
p[x] = find(p[x]); p[x] = find(p, p[x]);
return p[x]; return p[x];
} }
} }
// Call to function join(int x, int y) to join PARAM x and y
void join(int x, int y) { p[find(x)] = find(y); }
/**
* @brief Function to join
* @param [in,out] p array to join in
* @param x value or index to join to
* @param y value or index to join from
*/
void join(int *p, int x, int y) { p[find(p, x)] = find(p, y); }
/** Main function */
int main() int main()
{ {
// Have all array indexes that you need to use refrence themselves int union_set[MAX_SIZE];
// Have all array indexes that you need to use reference themselves
for (int i = 0; i < 10; i++) for (int i = 0; i < 10; i++)
{ {
p[i] = i; union_set[i] = i;
} }
// p = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9} // p = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
join(3, 5);
join(union_set, 3, 5);
printf("The array is now: ");
for (int i = 0; i < 10; i++)
{
printf("%d ", union_set[i]);
}
printf("\n");
// Now 3 and 5 are groupped together, that is find(3) = find(5) // Now 3 and 5 are groupped together, that is find(3) = find(5)
// p = {0, 1, 2, 5, 4, 5, 6, 7, 8, 9} // p = {0, 1, 2, 5, 4, 5, 6, 7, 8, 9}
join(3, 8);
join(union_set, 3, 8);
printf("The array is now: ");
for (int i = 0; i < 10; i++)
{
printf("%d ", union_set[i]);
}
printf("\n");
// Now 3, 5 and are groupped together, find(3) = find(5) = find(8) // Now 3, 5 and are groupped together, find(3) = find(5) = find(8)
// p = {0, 1, 2, 5, 4, 8, 6, 7, 8, 9} // p = {0, 1, 2, 5, 4, 8, 6, 7, 8, 9}
join(0, 5); join(union_set, 0, 5);
if (find(0) == find(3)) if (find(union_set, 0) == find(union_set, 3))
{ {
printf("0 and 3 are groupped together\n"); printf("0 and 3 are groupped together\n");
} }
printf("The array is now: "); printf("The array is now: ");
for (int i = 0; i < 10; i++) for (int i = 0; i < 10; i++)
{ {
printf("%d ", p[i]); printf("%d ", union_set[i]);
} }
printf("\n"); printf("\n");
return 0; return 0;
} }