Premier jet de la fonction sub_str, elle nous permettra de remonter d…

…ans l'espace de positions pour renvoyer le bon morceau de string. Elle sera appelée par gen_str (pas encore écrite, en cours de refléxion) Elle marche avec un alphabet de 2 char, faut juste gérer le cas d'une pass_len de 1. A essayer avec un alphabet plus grand.
stevenliatti · Nov 1, 2016 · 6ce1162 · 6ce1162
1 parent 140bfa8
commit 6ce1162
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Showing 2 changed files with 47 additions and 32 deletions.
diff --git a/src/test_steven/test_steven.c b/src/test_steven/test_steven.c
diff --git a/src/test_steven/test_sub_str.c b/src/test_steven/test_sub_str.c
@@ -0,0 1,47 @@
 #define _GNU_SOURCE
 #include <crypt.h>
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
 #include <stdbool.h>
 #include <assert.h>
 
 const int alphabet_size = 2;
 
 int pass_len(long position) {
  int i = 1;
  long min = 0;
  long max = (long) (pow(alphabet_size, i));
 
  while (!(min <= position && position < max)) {
  min = max;
  i ;
  max  = (long) (pow(alphabet_size, i));
  }
 
  return i;
 }
 
 long sub_str(int pass_len_actual, int pass_len_choose, long position) {
  if (pass_len_actual == pass_len_choose) {
  return position;
  }
  else {
  long past_position = (long) pow(alphabet_size, pass_len_actual - 1);
  long new_position = position - past_position;
  while (pass_len(new_position) == pass_len_actual) {
  new_position = new_position - past_position;
  }
  return sub_str(pass_len_actual - 1, pass_len_choose, new_position);
  }
 }
 
 int main() {
  for (int i = 30; i >= 0; i--) {
  int pass_len_actual = pass_len(i);
  int pass_len_choose = pass_len_actual - 1;
  long position = i;
  printf("De %d on va à %ld\n", i, sub_str(pass_len_actual, pass_len_choose, position));
  }
 }