Winter CS106B 2009
Handout 29S
Section Solution 6
February 18-20, 2009
Problem 1: Removing Duplicates
void RemoveDuplicates(node *list) { for (node *cur = list; cur != NULL; cur = if (cur->next != NULL && cur->value == node *duplicate = cur->next; cur->next = cur->next->next; delete duplicate; } } } cur->next) { cur->next->value) { // match? // remember // circumvent // dispose
Problem 2: Ribonucleic Acid and Codons
node **ExtractCodons(string rna, int counts[]) // counts is of length 4 { node **lists = new node *[4]; for (int i = 0; i < 4; i++) { counts[i] = 0; lists[i] = NULL; } for (int i = 0; i < rna.length(); i+=3) { string codon = rna.substr(i, 3); for (int j = 0; j < codon.length(); j++) counts[CharToIndex(codon[j])]++; int index = CharToIndex(codon[0]); *n node = new node; n->codon = codon; n->next = lists[index]; lists[index] = n; } return lists; } int CharToIndex(char ch) { switch (ch) { case 'A': return 0; case 'G': return 1; case 'U': return 2; case 'C': return 3; default: Error("Unexpected character: '%c'\n", ch); } }
2 Problem 3: Separating Odds And Evens!
struct node { int value; node *next; }; void SeparateOddsAndEvens(node *& list, node *& odds, node *& evens) { node **oddsp = &odds; // track the address of the original odds node **evensp = &evens; // same thing for the original evens for (node *curr = list; curr != NULL; curr = curr->next) { if (curr->value % 2 == 0) { *evensp = curr; evensp = &(curr->next); } else { *oddsp = curr; oddsp = &(curr->next); } } *oddsp = *evensp = list = NULL; }