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-rw-r--r--iterator_for_combination.c67
1 files changed, 67 insertions, 0 deletions
diff --git a/iterator_for_combination.c b/iterator_for_combination.c
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+// 1286. Iterator for Combination
+#include "leetcode.h"
+
+/*
+ * design the 'CombinationIterator' class:
+ * - 'CombinationIterator(string characters, int combinationLength)' initialises
+ * the object with a string 'characters' of sorted distinct lowercase english
+ * letters and a number 'combinationLength' as arguments
+ * - 'next()' returns the next combination of length 'combinationLength' in
+ * lexicographical order
+ * - 'hasNext()' returns 'true' iff there exists a next combination
+ */
+
+typedef struct c {
+ char *str;
+ struct c *next;
+} CombinationIterator;
+
+void get_comb(CombinationIterator **last, char *s, char *tab, int l, int len) {
+ if (l == len) {
+ (*last)->next = (CombinationIterator *)malloc(sizeof(CombinationIterator));
+ *last = (*last)->next;
+ (*last)->str = (char *)calloc(len + 1, 1);
+ while (l--)
+ ((*last)->str)[l] = tab[l];
+ (*last)->next = NULL;
+ } else if (!*s)
+ return;
+ else {
+ tab[l] = *s;
+ get_comb(last, s + 1, tab, l + 1, len);
+ get_comb(last, s + 1, tab, l, len);
+ }
+}
+
+CombinationIterator *combinationIteratorCreate(char *characters,
+ int combinationLength) {
+ CombinationIterator *cmb =
+ (CombinationIterator *)malloc(sizeof(CombinationIterator));
+ cmb->next = NULL;
+ CombinationIterator *p = cmb;
+ char tab[combinationLength + 1];
+ get_comb(&p, characters, tab, 0, combinationLength);
+ return cmb;
+}
+
+char *combinationIteratorNext(CombinationIterator *obj) {
+ char *p = obj->next->str;
+ obj->next = obj->next->next;
+ return p;
+}
+
+bool combinationIteratorHasNext(CombinationIterator *obj) { return obj->next; }
+
+void combinationIteratorFree(CombinationIterator *obj) { free(obj); }
+
+int main() {
+ char *characters = "abc";
+ CombinationIterator *obj = combinationIteratorCreate(characters, 2);
+ printf("%s\n", combinationIteratorNext(obj)); // expect: ab
+ printf("%d\n", combinationIteratorHasNext(obj)); // expect: 1
+ printf("%s\n", combinationIteratorNext(obj)); // expect: ac
+ printf("%d\n", combinationIteratorHasNext(obj)); // expect: 1
+ printf("%s\n", combinationIteratorNext(obj)); // expect: bc
+ printf("%d\n", combinationIteratorHasNext(obj)); // expect: 0
+ combinationIteratorFree(obj);
+}