diff --git a/C/p018.c b/C/p018.c index 83e51a6..c89bf0b 100644 --- a/C/p018.c +++ b/C/p018.c @@ -1,14 +1,41 @@ +/* By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23. + * + * 3 + * 7 4 + * 2 4 6 + * 8 5 9 3 + * + * That is, 3 + 7 + 4 + 9 = 23. + * + * Find the maximum total from top to bottom of the triangle below: + * + * 75 + * 95 64 + * 17 47 82 + * 18 35 87 10 + * 20 04 82 47 65 + * 19 01 23 75 03 34 + * 88 02 77 73 07 63 67 + * 99 65 04 28 06 16 70 92 + * 41 41 26 56 83 40 80 70 33 + * 41 48 72 33 47 32 37 16 94 29 + * 53 71 44 65 25 43 91 52 97 51 14 + * 70 11 33 28 77 73 17 78 39 68 17 57 + * 91 71 52 38 17 14 91 43 58 50 27 29 48 + * 63 66 04 68 89 53 67 30 73 16 69 87 40 31 + * 04 62 98 27 23 09 70 98 73 93 38 53 60 04 23 + * + * NOTE: As there are only 16384 routes, it is possible to solve this problem by trying every route. However, Problem 67, is the same challenge + * with a triangle containing one-hundred rows; it cannot be solved by brute force, and requires a clever method! ;o)*/ + #include #include #include - -void sum_triangle(int **triang, int n, int i, int j, int sum); - -int max = 0; +#include "projecteuler.h" int main(int argc, char **argv) { - int i, j; + int i, j, max; int **triang; double elapsed; FILE *fp; @@ -47,7 +74,7 @@ int main(int argc, char **argv) fclose(fp); - sum_triangle(triang, 15, 0, 0, 0); + max = find_max_path(triang, 15); clock_gettime(CLOCK_MONOTONIC, &end); @@ -60,19 +87,3 @@ int main(int argc, char **argv) return 0; } - -void sum_triangle(int **triang, int n, int i, int j, int sum) -{ - if(i == n) - { - if(sum > max) - { - max = sum; - } - return; - } - - sum_triangle(triang, n, i+1, j, sum+triang[i][j]); - sum_triangle(triang, n, i+1, j+1, sum+triang[i][j]); - -} diff --git a/C/projecteuler.c b/C/projecteuler.c index b98870a..40074e7 100644 --- a/C/projecteuler.c +++ b/C/projecteuler.c @@ -188,6 +188,24 @@ int count_divisors(int n) return count; } +int find_max_path(int **triang, int n) +{ + int i, j; + + for(i = n - 2; i >= 0; i--) + { + for(j = 0; j <= i; j++) + { + if(triang[i+1][j] > triang[i+1][j+1]) + triang[i][j] += triang[i+1][j]; + else + triang[i][j] += triang[i+1][j+1]; + } + } + + return triang[0][0]; +} + void insertion_sort(void **array, int l, int r, int (*cmp)(void *lv, void *rv)) { int i, j; diff --git a/C/projecteuler.h b/C/projecteuler.h index dedc2c0..af9f2f5 100644 --- a/C/projecteuler.h +++ b/C/projecteuler.h @@ -8,6 +8,7 @@ long int lcm(long int a, long int b); long int lcmm(long int *values, int n); int *sieve(int n); int count_divisors(int n); +int find_max_path(int **triang, int n); void insertion_sort(void **array, int l, int r, int (*cmp)(void *lv, void *rv)); void quick_sort(void **array, int l, int r, int (*cmp)(void *lv, void *rv)); int is_pandigital(int value, int n);