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Krishna Vedala 2020-04-02 13:15:25 -04:00
parent 50a113addb
commit f34164e601
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2 changed files with 19 additions and 2 deletions
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6
project_euler/Problem 23/sol1.c
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@ -38,7 +38,7 @@ char get_perfect_number(unsigned long N)
}
/**
* Find the next abundant number after N and not including N
* Is the given number an abundant number (1) or not (0)
**/
unsigned long is_abundant(unsigned long N)
{
@ -64,6 +64,10 @@ unsigned long get_next_abundant(unsigned long N)
**/
char is_sum_of_abundant(unsigned long N)
{
/** optimized logic:
* i + j = N where both i and j should be abundant
* hence we can simply check for j = N - i as we loop through i
**/
for (unsigned long i = get_next_abundant(1); i <= (N >> 1); i = get_next_abundant(i))
if (is_abundant(N - i))
{

15
project_euler/Problem 23/sol2.c
View File

@ -12,6 +12,14 @@
**/
unsigned long MAX_N = 28123;
/**
* This is the global array to be used to store a flag to identify
* if a particular number is abundant (1) or not (0).
* Using a whole byte to store a binary info would be redundant.
* We will use each byte to represent 8 numbers by relying on bits.
* This saves memory required by 1/8
**/
char *abundant_flags = NULL;
/**
@ -44,7 +52,7 @@ char get_perfect_number(unsigned long N)
}
/**
* Find the next abundant number after N and not including N
* Is the given number an abundant number (1) or not (0)
**/
char is_abundant(unsigned long N)
{
@ -58,6 +66,7 @@ char is_abundant(unsigned long N)
unsigned long get_next_abundant(unsigned long N)
{
unsigned long i;
/* keep checking successive numbers till an abundant number is found */
for (i = N + 1; !is_abundant(i); ++i)
;
return i;
@ -71,6 +80,10 @@ unsigned long get_next_abundant(unsigned long N)
**/
char is_sum_of_abundant(unsigned long N)
{
/** optimized logic:
* i + j = N where both i and j should be abundant
* hence we can simply check for j = N - i as we loop through i
**/
for (unsigned long i = get_next_abundant(1); i <= (N >> 1); i = get_next_abundant(i))
if (is_abundant(N - i))
{