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  1. //
  2. // stack, array, static node, recursive
  3. //
  4. #include <stdio.h>
  5. #include <stdlib.h>
  6. #include <string.h>
  7.  
  8. long long int recursive1(long long int n) {
  9.     if (n == 0)
  10.         return n;
  11.  
  12.     //printf("%zd\n",n);
  13.     return n + recursive1(n-1);
  14. }
  15.  
  16. //========================================================//
  17.  
  18. long long int recursive2(int n) {
  19.     size_t current;
  20.     size_t length;
  21.  
  22.     struct node {
  23.         long int n;
  24.         int step;
  25.     };
  26.  
  27.     static struct node nodes[64000000];
  28.     struct node node;        
  29.  
  30.     long long int rvalue;
  31.  
  32.     length = 0;
  33.     current = 0;
  34.  
  35.     node.n = n;
  36.     node.step = 0;
  37.     //rvalue = 0;
  38.  
  39.     nodes[length] = node;
  40.     length++;
  41.  
  42.     while (length > 0) {
  43.         current = length-1;
  44.         if (nodes[current].step == 0) {
  45.             if (nodes[current].n == 0) {
  46.                 rvalue = 0;
  47.                 length--;
  48.                 continue;
  49.             }
  50.  
  51.             //printf("%ld\n", nodes[current].n);
  52.  
  53.             nodes[length - 1].step++;
  54.  
  55.             nodes[length].n = nodes[current].n - 1;
  56.             nodes[length].step = nodes[current].step - 1;
  57.             length++;
  58.         } else if (nodes[current].step == 1) {
  59.             rvalue += nodes[current].n;
  60.             length--;
  61.         }
  62.     }
  63.     return rvalue;
  64. }
  65.  
  66. //========================================================//
  67.  
  68. int main(void) {
  69.  
  70.     //printf("recursive1(): %lld;\n\n", recursive1(50000000));
  71.     printf("recursive2(): %lld;\n\n", recursive2(50000000));
  72.  
  73.     return 0;
  74. }
  75.  
Success #stdin #stdout 0.61s 502272KB
comments (?)
stdin 
Standard input is empty
stdout 
recursive2(): 1250000025000000;
https://ideone.com/u5P3ux
language:
C (gcc 8.3)
created:
11 years ago
visibility:
secret

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