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43 * @file hash_resize_example.cpp
44 * An example of externally resizing a map.
48 * This example shows how to externally manipulate the size of a hash-based
49 * container object throught its resize-policy object.
54 #include <ext/pb_ds/assoc_container.hpp>
55 #include <ext/pb_ds/hash_policy.hpp>
58 using namespace __gnu_pbds
;
60 // A simple hash functor.
61 // hash could serve instead of this functor, but it is not yet
62 // standard everywhere.
63 struct int_hash
: public unary_function
<int, size_t>
66 operator()(const int& r_i
) const
72 // A probing hash table mapping ints to chars.
80 // Combining function.
81 direct_mask_range_hashing
<>,
85 hash_standard_resize_policy
<
86 hash_exponential_size_policy
<>,
87 hash_load_check_resize_trigger
<>,
88 /* Allow external access to size.
89 * Without setting this to true, external resizing
97 // Check the actual size of the container object. In this case, this
98 // should be the initial size given by the size policy object.
99 assert(g
.get_actual_size() == 8);
101 // Insert some elements.
106 // Now resize the table upward.
109 // Check the actual size of the container object.
110 // For the policy used in this example, the nearest larger size than
112 assert(g
.get_actual_size() == 256);
117 // Regardless of the internal size, the logical size should be 5.
118 assert(g
.size() == 5);
120 // Now resize the table downward.
123 // Check the actual size of the container object.
124 // For the policy used in this example, the nearest larger size than
126 assert(g
.get_actual_size() == 128);
130 // Regardless of the internal size, the logical size should be 5.
131 assert(g
.size() == 6);