Random tree generation always creating regular tree
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I have been doing experiments with tree algorithms in C. To check their correctness I have implemented a simple function to generate random binary trees. Somehow it seems that all the generated trees are regular, meaning that the tree is "full" and has exactly (2^height)-1 nodes.
I start at the root node and with a certain probability call the function recursively on left and right child. The function also has a depth limit. The created tree does not always have the full height, but it is always regular. My guess is that something is wrong with my random number generator.
#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
/* tree node; data left out for brevity */
typedef struct node {
struct node *left, *right;
} Node;
/* simple helper function to print a tree */
void _print_tree(Node *node, int lvl) {
if (!node) return;
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("r");
_print_tree(node->right, lvl+1);
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("l");
_print_tree(node->right, lvl+1);
}
void print_tree(Node *root) {
_print_tree(root, 0);
}
/* make random tree with a given probability of creating a child
node and given maximum depth / height of the tree */
Node *make_random_tree(double prob, int maxdepth) {
Node *root = NULL;
if (maxdepth--)
root = calloc(1, sizeof(Node));
if (root) {
if (rand() < (double) RAND_MAX * prob)
root->left = make_random_tree(prob, maxdepth);
if (rand() < (double) RAND_MAX * prob)
root->right = make_random_tree(prob, maxdepth);
}
return root;
}
int main(int argc, char *argv) {
double prob = 0.5;
int maxdepth = 20;
if (argc > 1) {
char *ep;
prob = strtod(argv[1], &ep);
if (*ep) return 1;
}
if (argc > 2) {
char *ep;
maxdepth = strtol(argv[2], &ep, 10);
if (*ep) return 1;
}
/* random number generator is initialized properly?! */
struct timeval tv;
gettimeofday(&tv, NULL);
unsigned int seed = tv.tv_sec ^ tv.tv_usec;
srand(seed);
Node *tree = make_random_tree(prob, maxdepth);
print_tree(tree);
}
c tree random
asked 4 hours ago
streptococotte
1
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I have been doing experiments with tree algorithms in C. To check their correctness I have implemented a simple function to generate random binary trees. Somehow it seems that all the generated trees are regular, meaning that the tree is "full" and has exactly (2^height)-1 nodes.
I start at the root node and with a certain probability call the function recursively on left and right child. The function also has a depth limit. The created tree does not always have the full height, but it is always regular. My guess is that something is wrong with my random number generator.
#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
/* tree node; data left out for brevity */
typedef struct node {
struct node *left, *right;
} Node;
/* simple helper function to print a tree */
void _print_tree(Node *node, int lvl) {
if (!node) return;
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("r");
_print_tree(node->right, lvl+1);
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("l");
_print_tree(node->right, lvl+1);
}
void print_tree(Node *root) {
_print_tree(root, 0);
}
/* make random tree with a given probability of creating a child
node and given maximum depth / height of the tree */
Node *make_random_tree(double prob, int maxdepth) {
Node *root = NULL;
if (maxdepth--)
root = calloc(1, sizeof(Node));
if (root) {
if (rand() < (double) RAND_MAX * prob)
root->left = make_random_tree(prob, maxdepth);
if (rand() < (double) RAND_MAX * prob)
root->right = make_random_tree(prob, maxdepth);
}
return root;
}
int main(int argc, char *argv) {
double prob = 0.5;
int maxdepth = 20;
if (argc > 1) {
char *ep;
prob = strtod(argv[1], &ep);
if (*ep) return 1;
}
if (argc > 2) {
char *ep;
maxdepth = strtol(argv[2], &ep, 10);
if (*ep) return 1;
}
/* random number generator is initialized properly?! */
struct timeval tv;
gettimeofday(&tv, NULL);
unsigned int seed = tv.tv_sec ^ tv.tv_usec;
srand(seed);
Node *tree = make_random_tree(prob, maxdepth);
print_tree(tree);
}
c tree random
asked 4 hours ago
streptococotte
1
New contributor
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
More normal to do:srand(time())
– Martin York
3 hours ago
Yes, but that gives you the same results for all runs within a second.
– streptococotte
3 hours ago
add a comment |
up vote
0
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up vote
0
down vote
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I have been doing experiments with tree algorithms in C. To check their correctness I have implemented a simple function to generate random binary trees. Somehow it seems that all the generated trees are regular, meaning that the tree is "full" and has exactly (2^height)-1 nodes.
I start at the root node and with a certain probability call the function recursively on left and right child. The function also has a depth limit. The created tree does not always have the full height, but it is always regular. My guess is that something is wrong with my random number generator.
#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
/* tree node; data left out for brevity */
typedef struct node {
struct node *left, *right;
} Node;
/* simple helper function to print a tree */
void _print_tree(Node *node, int lvl) {
if (!node) return;
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("r");
_print_tree(node->right, lvl+1);
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("l");
_print_tree(node->right, lvl+1);
}
void print_tree(Node *root) {
_print_tree(root, 0);
}
/* make random tree with a given probability of creating a child
node and given maximum depth / height of the tree */
Node *make_random_tree(double prob, int maxdepth) {
Node *root = NULL;
if (maxdepth--)
root = calloc(1, sizeof(Node));
if (root) {
if (rand() < (double) RAND_MAX * prob)
root->left = make_random_tree(prob, maxdepth);
if (rand() < (double) RAND_MAX * prob)
root->right = make_random_tree(prob, maxdepth);
}
return root;
}
int main(int argc, char *argv) {
double prob = 0.5;
int maxdepth = 20;
if (argc > 1) {
char *ep;
prob = strtod(argv[1], &ep);
if (*ep) return 1;
}
if (argc > 2) {
char *ep;
maxdepth = strtol(argv[2], &ep, 10);
if (*ep) return 1;
}
/* random number generator is initialized properly?! */
struct timeval tv;
gettimeofday(&tv, NULL);
unsigned int seed = tv.tv_sec ^ tv.tv_usec;
srand(seed);
Node *tree = make_random_tree(prob, maxdepth);
print_tree(tree);
}
c tree random
asked 4 hours ago
streptococotte
1
New contributor
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I have been doing experiments with tree algorithms in C. To check their correctness I have implemented a simple function to generate random binary trees. Somehow it seems that all the generated trees are regular, meaning that the tree is "full" and has exactly (2^height)-1 nodes.
I start at the root node and with a certain probability call the function recursively on left and right child. The function also has a depth limit. The created tree does not always have the full height, but it is always regular. My guess is that something is wrong with my random number generator.
#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
/* tree node; data left out for brevity */
typedef struct node {
struct node *left, *right;
} Node;
/* simple helper function to print a tree */
void _print_tree(Node *node, int lvl) {
if (!node) return;
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("r");
_print_tree(node->right, lvl+1);
for (int i=0; i<lvl; i++) printf("%3s", "");
puts("l");
_print_tree(node->right, lvl+1);
}
void print_tree(Node *root) {
_print_tree(root, 0);
}
/* make random tree with a given probability of creating a child
node and given maximum depth / height of the tree */
Node *make_random_tree(double prob, int maxdepth) {
Node *root = NULL;
if (maxdepth--)
root = calloc(1, sizeof(Node));
if (root) {
if (rand() < (double) RAND_MAX * prob)
root->left = make_random_tree(prob, maxdepth);
if (rand() < (double) RAND_MAX * prob)
root->right = make_random_tree(prob, maxdepth);
}
return root;
}
int main(int argc, char *argv) {
double prob = 0.5;
int maxdepth = 20;
if (argc > 1) {
char *ep;
prob = strtod(argv[1], &ep);
if (*ep) return 1;
}
if (argc > 2) {
char *ep;
maxdepth = strtol(argv[2], &ep, 10);
if (*ep) return 1;
}
/* random number generator is initialized properly?! */
struct timeval tv;
gettimeofday(&tv, NULL);
unsigned int seed = tv.tv_sec ^ tv.tv_usec;
srand(seed);
Node *tree = make_random_tree(prob, maxdepth);
print_tree(tree);
}
c tree random
c tree random
asked 4 hours ago
streptococotte
1
New contributor
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
streptococotte
1
New contributor
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
streptococotte
1
New contributor
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
streptococotte
1
asked 4 hours ago
streptococotte
1
1
New contributor
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
streptococotte is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
More normal to do:srand(time())
– Martin York
3 hours ago
Yes, but that gives you the same results for all runs within a second.
– streptococotte
3 hours ago
add a comment |
More normal to do:srand(time())
– Martin York
3 hours ago
Yes, but that gives you the same results for all runs within a second.
– streptococotte
3 hours ago
More normal to do:
srand(time())– Martin York
3 hours ago
More normal to do:
srand(time())– Martin York
3 hours ago
Yes, but that gives you the same results for all runs within a second.
– streptococotte
3 hours ago
Yes, but that gives you the same results for all runs within a second.
– streptococotte
3 hours ago
add a comment |
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More normal to do:
srand(time())– Martin York
3 hours ago
Yes, but that gives you the same results for all runs within a second.
– streptococotte
3 hours ago