234 lines
6.9 KiB
C
234 lines
6.9 KiB
C
/**
|
|
* iterator.c
|
|
*
|
|
* Creation Date: 14/05/2019
|
|
*
|
|
* Authors:
|
|
* Leonardo Vencovsky (https://github.com/LeoVen)
|
|
*
|
|
* Iterator Example
|
|
*/
|
|
#include "cmc/hashmap.h"
|
|
#include <stdio.h>
|
|
#include <inttypes.h>
|
|
|
|
// Int hash function
|
|
size_t inthash(int t)
|
|
{
|
|
size_t a = t;
|
|
a += ~(a << 15);
|
|
a ^= (a >> 10);
|
|
a += (a << 3);
|
|
a ^= (a >> 6);
|
|
a += ~(a << 11);
|
|
a ^= (a >> 16);
|
|
return a;
|
|
}
|
|
|
|
// Int compare function
|
|
int intcmp(int a, int b)
|
|
{
|
|
return a - b;
|
|
}
|
|
|
|
// Creates a hashmap of integers
|
|
CMC_GENERATE_HASHMAP(hm, hashmap, int, double);
|
|
typedef struct hashmap hashmap;
|
|
typedef struct hashmap_iter hashmap_iter;
|
|
|
|
|
|
int main(int argc, char const *argv[])
|
|
{
|
|
// Create a new hashmap with an initial capacity of 100 and load factor of 0.6
|
|
hashmap *my_map = hm_new(100, 0.6, intcmp, inthash);
|
|
|
|
// Add pairs to the hashmap
|
|
for (int i = 0; i < 20; i++)
|
|
{
|
|
// Map integers to doubles
|
|
hm_insert(my_map, i, (double)i / 10.0);
|
|
}
|
|
|
|
// Iterate from the start (index 0) to the end (index count - 1) of the hashmap
|
|
for (hashmap_iter it = my_map->it_start(my_map); // Initialize iterator 'it' to the start of the hashmap
|
|
!hm_iter_end(&it); // Conditional stop (until it is not at the end)
|
|
hm_iter_next(&it)) // Iterator goes one position forward
|
|
{
|
|
// Access the current key
|
|
int k = hm_iter_key(&it);
|
|
|
|
// Access the current value
|
|
double v = hm_iter_value(&it);
|
|
|
|
// Access the current index (index is relative to all the pairs in the iteration)
|
|
size_t i = hm_iter_index(&it);
|
|
|
|
// Print hashmap
|
|
|
|
// Index is useful in situations like this
|
|
// If it is the first pair
|
|
if (i == 0)
|
|
printf("[ {%d:%.2lf}, ", k, v);
|
|
// If it is the last pair
|
|
else if (i == hm_count(my_map) - 1)
|
|
printf("{%d:%.2lf} ]\n", k, v);
|
|
// For pairs at the middle
|
|
else
|
|
printf("{%d:%.2lf}, ", k, v);
|
|
}
|
|
|
|
// Index can also be used to iterate over a certain portion of a collection
|
|
size_t limit = hm_count(my_map) / 2;
|
|
for (hashmap_iter it = my_map->it_start(my_map); !hm_iter_end(&it); hm_iter_next(&it))
|
|
{
|
|
// Access the current key
|
|
int k = hm_iter_key(&it);
|
|
|
|
// Access the current value
|
|
double v = hm_iter_value(&it);
|
|
|
|
// Access the current index (index is relative to all the pairs in the iteration)
|
|
size_t i = hm_iter_index(&it);
|
|
|
|
// Print hashmap up until limit
|
|
|
|
// If it is the first pair
|
|
if (i == 0)
|
|
printf("[ {%d:%.2lf}, ", k, v);
|
|
// If it is the last pair
|
|
else if (i == limit - 1) // -1 because index is 0 based and we want half of the hashmap
|
|
{
|
|
printf("{%d:%.2lf} ]\n", k, v);
|
|
break;
|
|
}
|
|
// For pairs at the middle
|
|
else
|
|
printf("{%d:%.2lf}, ", k, v);
|
|
}
|
|
|
|
// Going backwards
|
|
for (hashmap_iter it = my_map->it_end(my_map); // Initialize iterator 'it' to the end of the hashmap
|
|
!hm_iter_start(&it); // Conditional stop (until it is not at the start)
|
|
hm_iter_prev(&it)) // Iterator goes one position backwards
|
|
{
|
|
// Access the current key
|
|
int k = hm_iter_key(&it);
|
|
|
|
// Access the current value
|
|
double v = hm_iter_value(&it);
|
|
|
|
// Access the current index (index is relative to all the pairs in the iteration)
|
|
size_t i = hm_iter_index(&it);
|
|
|
|
// Print hashmap
|
|
// Note how the conditions for the first and last pairs are simply swapped
|
|
// Because iterating backwards make the first pair be the index count - 1
|
|
// and the last one be the index 0
|
|
|
|
// If it is the first pair
|
|
if (i == hm_count(my_map) - 1)
|
|
printf("[ {%d:%.2lf}, ", k, v);
|
|
// If it is the last pair
|
|
else if (i == 0)
|
|
printf("{%d:%.2lf} ]\n", k, v);
|
|
// For pairs at the middle
|
|
else
|
|
printf("{%d:%.2lf}, ", k, v);
|
|
}
|
|
|
|
// You can also use iterators in a while loop
|
|
// But to do so you must declare the iterator struct outside the loop first
|
|
hashmap_iter it;
|
|
|
|
// You have three options:
|
|
// - Initialize it using the functions provided by the hashmap [ my_map->it_start() and my_map->it_end() ]
|
|
// - Initialize it using the init() function (when the iterator is already allocated)
|
|
// - Initialize it using the new() function (allocates on the heap, pointers only)
|
|
|
|
it = my_map->it_start(my_map);
|
|
it = my_map->it_end(my_map);
|
|
|
|
// This is equivalent to it_start()
|
|
hm_iter_init(&it, my_map);
|
|
|
|
// For pointers
|
|
// Also equivalent to it_start()
|
|
hashmap_iter *iter = hm_iter_new(my_map);
|
|
|
|
// The actual while loop
|
|
while (!hm_iter_end(iter))
|
|
{
|
|
// Accessing pairs
|
|
int k = hm_iter_key(iter);
|
|
double v = hm_iter_value(iter);
|
|
size_t i = hm_iter_index(iter);
|
|
|
|
// Print index and key value pair
|
|
printf("hashmap[%2" PRIuMAX "] = { %2d : %.2lf }\n", i, k, v);
|
|
|
|
// Move iterator forwards
|
|
hm_iter_next(iter);
|
|
}
|
|
|
|
// Send the iterator to the start of the hashmap
|
|
hm_iter_to_start(iter);
|
|
|
|
// Send the iterator to the end of the hashmap
|
|
hm_iter_to_end(iter);
|
|
|
|
// Backwards loop
|
|
while (!hm_iter_start(iter))
|
|
{
|
|
// Accessing pairs
|
|
int k = hm_iter_key(iter);
|
|
double v = hm_iter_value(iter);
|
|
size_t i = hm_iter_index(iter);
|
|
|
|
// Print index and the key value pair
|
|
printf("hashmap[%2" PRIuMAX "] = { %2d : %.2lf }\n", i, k, v);
|
|
|
|
// Move iterator backwards
|
|
hm_iter_prev(iter);
|
|
}
|
|
|
|
// Certain iterators also allow you to modify the contents it is iterating over
|
|
// Exceptions are collections that depend of the current state of the pair
|
|
// like tree-based collections and heap (collections that have some kind of ordering).
|
|
// You also can't change the keys of an associative collection
|
|
|
|
// Change every value where its key is divisible by 3 to the number 7
|
|
for (hm_iter_to_start(&it); !hm_iter_end(&it); hm_iter_next(&it))
|
|
{
|
|
// Get current key
|
|
int k = hm_iter_key(&it);
|
|
|
|
// Get a reference to the current value
|
|
double *v = hm_iter_rvalue(&it);
|
|
|
|
if (k % 3 == 0)
|
|
*v = 7;
|
|
}
|
|
|
|
// Now print it to see the difference
|
|
for (hashmap_iter it = my_map->it_start(my_map); !hm_iter_end(&it); hm_iter_next(&it))
|
|
{
|
|
int k = hm_iter_key(&it);
|
|
double v = hm_iter_value(&it);
|
|
size_t i = hm_iter_index(&it);
|
|
|
|
if (i == 0)
|
|
printf("[ {%d:%.2lf}, ", k, v);
|
|
else if (i == hm_count(my_map) - 1)
|
|
printf("{%d:%.2lf} ]\n", k, v);
|
|
else
|
|
printf("{%d:%.2lf}, ", k, v);
|
|
}
|
|
|
|
// Dispose the iterator called by hm_iter_new()
|
|
hm_iter_free(iter);
|
|
// Dispose the hashmap created
|
|
hm_free(my_map, NULL);
|
|
|
|
return 0;
|
|
}
|