Add more solutions

Added solutions for problems 26, 27, 28, 29 and 30, both in C
and python

C/p026.c

@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <time.h>
+#include <gmp.h>
+
+int main(int argc, char **argv)
+{
+   int i, j, n, max = 0, max_n = 0;
+   double elapsed;
+   struct timespec start, end;
+   mpz_t k, div;
+
+   clock_gettime(CLOCK_MONOTONIC, &start);
+
+   mpz_init(k);
+   mpz_init(div);
+
+   for(i = 2; i < 1000; i++)
+   {
+      j = i;
+
+      while(j % 2 == 0 && j > 1)
+         j /= 2;
+
+      while(j % 5 == 0 && j > 1)
+         j /= 5;
+
+      mpz_set_ui(k, 9);
+
+      if(j == 1)
+         n = 0;
+      else
+      {
+         n = 1;
+
+         mpz_set_ui(div, j);
+
+         while(!mpz_divisible_p(k, div))
+         {
+            n++;
+            mpz_mul_ui(k, k, 10);
+            mpz_add_ui(k, k, 9);
+         }
+
+         if(n > max)
+         {
+            max = n;
+            max_n = i;
+         }
+      }
+   }
+
+   mpz_clears(k, div, NULL);
+
+   clock_gettime(CLOCK_MONOTONIC, &end);
+
+   elapsed=(end.tv_sec-start.tv_sec)+(double)(end.tv_nsec-start.tv_nsec)/1000000000;
+
+   printf("Project Euler, Problem 26\n");
+   printf("Answer: %d\n", max_n);
+
+   printf("Elapsed time: %.9lf seconds\n", elapsed);
+
+   return 0;
+}

C/p027.c

@@ -0,0 +1,56 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <time.h>
+#include "projecteuler.h"
+
+int main(int argc, char **argv)
+{
+   int a, b, n, p, count, max = 0, save_a, save_b;
+   double elapsed;
+   struct timespec start, end;
+
+   clock_gettime(CLOCK_MONOTONIC, &start);
+
+   for(a = -999; a < 1000; a++)
+   {
+      for(b = 2; b <= 1000; b++)
+      {
+         n = 0;
+         count = 0;
+
+         while(1)
+         {
+            p = n * n + a * n + b;
+
+            if(p > 1 && is_prime(p))
+            {
+               count++;
+               n++;
+            }
+            else
+            {
+               break;
+            }
+         }
+
+         if(count > max)
+         {
+            max = count;
+            save_a = a;
+            save_b = b;
+         }
+      }
+   }
+
+   clock_gettime(CLOCK_MONOTONIC, &end);
+
+   elapsed = (end.tv_sec - start.tv_sec) + (double)(end.tv_nsec - start.tv_nsec) / 1000000000;
+
+   printf("Project Euler, Problem 27\n");
+   printf("Answer: %d\n", save_a * save_b);
+
+   printf("Elapsed time: %.9lf seconds\n", elapsed);
+
+   return 0;
+}

C/p028.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define N 1001
+
+int main(int argc, char **argv)
+{
+   int i, j, step = 0, limit = N * N, sum = 1;
+   double elapsed;
+   struct timespec start, end;
+
+   clock_gettime(CLOCK_MONOTONIC, &start);
+
+   for(i = 0, j = 1; j < limit; i = (i + 1) % 4)
+   {
+      if(i == 0)
+      {
+         step += 2;
+      }
+
+      j += step;
+      sum += j;
+   }
+
+   clock_gettime(CLOCK_MONOTONIC, &end);
+
+   elapsed = (end.tv_sec - start.tv_sec) + (double)(end.tv_nsec - start.tv_nsec) / 1000000000;
+
+   printf("Project Euler, Problem 28\n");
+   printf("Answer: %d\n", sum);
+
+   printf("Elapsed time: %.9lf seconds\n", elapsed);
+
+   return 0;
+}

C/p029.c

@@ -0,0 +1,87 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <gmp.h>
+
+void selection_sort(mpz_t *v, int n);
+
+int main(int argc, char **argv)
+{
+   mpz_t a;
+   mpz_t powers[9801];
+   int i, j, count;
+   double elapsed;
+   struct timespec start, end;
+
+   clock_gettime(CLOCK_MONOTONIC, &start);
+
+   mpz_init(a);
+
+   for(i = 0; i < 9801; i++)
+   {
+      mpz_init(powers[i]);
+   }
+
+   for(i = 2; i <= 100; i++)
+   {
+      mpz_set_ui(a, i);
+      for(j = 2; j <= 100; j++)
+      {
+         mpz_pow_ui(powers[(i-2)*99+j-2], a, j);
+      }
+   }
+
+   mpz_clear(a);
+
+   selection_sort(powers, 9801);
+   count = 1;
+
+   for(i = 1; i < 9801; i++)
+   {
+      if(mpz_cmp(powers[i], powers[i-1]))
+      {
+         count++;
+      }
+   }
+
+   for(i = 0; i < 9801; i++)
+   {
+      mpz_clear(powers[i]);
+   }
+
+   clock_gettime(CLOCK_MONOTONIC, &end);
+
+   elapsed = (end.tv_sec - start.tv_sec) + (double)(end.tv_nsec - start.tv_nsec) / 1000000000;
+
+   printf("Project Euler, Problem 29\n");
+   printf("Answer: %d\n", count);
+
+   printf("Elapsed time: %.9lf seconds\n", elapsed);
+
+   return 0;
+}
+
+void selection_sort(mpz_t *v, int n)
+{
+   int i, j, min;
+   mpz_t tmp;
+
+   mpz_init(tmp);
+
+   for(i = 0; i < n - 1; i++)
+   {
+      min = i;
+      
+      for(j = i + 1; j < n; j++)
+      {
+         if(mpz_cmp(v[j], v[min])<0)
+         {
+            min = j;
+         }
+      }
+
+      mpz_set(tmp, v[min]);
+      mpz_set(v[min], v[i]);
+      mpz_set(v[i], tmp);
+   }
+}

C/p030.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <time.h>
+
+int main(int argc, char **argv)
+{
+   int i, j, digit, sum, sum_tot = 0;
+   double elapsed;
+   struct timespec start, end;
+
+   clock_gettime(CLOCK_MONOTONIC, &start);
+
+   for(i = 10; i < 354295; i++)
+   {
+      j = i;
+      sum = 0;
+
+      while(j > 0)
+      {
+         digit = j % 10;
+         sum += (pow(digit, 5));
+         j /= 10;
+      }
+
+      if(sum == i)
+      {
+         sum_tot += i;
+      }
+   }
+
+   clock_gettime(CLOCK_MONOTONIC, &end);
+
+   elapsed=(end.tv_sec-start.tv_sec)+(double)(end.tv_nsec-start.tv_nsec)/1000000000;
+
+   printf("Project Euler, problem 30\n");
+   printf("Answer: %d\n", sum_tot);
+
+   printf("Elapsed time: %.9lf seconds\n", elapsed);
+
+   return 0;
+}