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+// 638. Shopping Offers
+#include "leetcode.h"
+
+/*
+ * in leetcode store, there are 'n' items to sell. each item has a price.
+ * however, there are some special offers, and a special offer consists of one
+ * or more different kinds of items with a sale price. you are given an integer
+ * array 'price' where 'price[i]' is the price of the i'th item, and an integer
+ * array 'needs' where 'needs[i]' is the number of pieces the i'th item you want
+ * to buy. you are also given an array 'special', where 'special[i]' is of size
+ * 'n + 1' where 'special[i][j]' is the number of pieces of the j'th item in the
+ * i'th other. return the lowest price you have to pay for exactly certain items
+ * as given, where you could make optimal use of the special offers. you are not
+ * allowed to buy more items that you want, even if that would lower the overall
+ * price.
+ */
+
+#define MOD 1009
+
+struct node {
+ struct node *next;
+ int key;
+ int val;
+};
+
+struct node *hash[MOD];
+
+void hash_init(void) { memset((void *)hash, 0, sizeof(hash)); }
+
+void hash_push(int key, int val) {
+ int idx = key % MOD;
+ struct node *tmp = (struct node *)malloc(sizeof(struct node));
+ tmp->key = key;
+ tmp->val = val;
+ tmp->next = hash[idx];
+ hash[idx] = tmp;
+}
+
+int hash_pop(int key) {
+ int idx = key % MOD;
+ struct node *tmp = hash[idx];
+ for (; tmp; tmp = tmp->next)
+ if (tmp->key == key)
+ return tmp->val;
+ return -1;
+}
+
+void hash_free(void) {
+ for (int i = 0; i < MOD; i++)
+ for (struct node *tmp = hash[i], *del; tmp;) {
+ del = tmp;
+ tmp = tmp->next;
+ free(del);
+ }
+}
+
+int lowest_price(int n, int need, int *prices, int **special, int specialSize,
+ int *specialColSize) {
+ int min = INT_MAX, price = 0, tmp;
+ bool accept = true;
+ if (!need)
+ return 0;
+ price = hash_pop(need);
+ if (price >= 0)
+ return price;
+ price = 0;
+ tmp = need;
+ for (int i = 0; i < n; i++) {
+ price += prices[i] * (tmp & 0x0F);
+ tmp >>= 4;
+ }
+ min = fmin(min, price);
+ for (int i = 0; i < specialSize; i++) {
+ tmp = need;
+ accept = true;
+ for (int j = 0; j < n; j++) {
+ int quantity = (tmp >> (j * 4)) & 0x0F;
+ if (quantity >= special[i][j]) {
+ quantity -= special[i][j];
+ tmp &= ~(0x0F << (j * 4));
+ tmp |= (quantity << (j * 4));
+ } else {
+ accept = false;
+ break;
+ }
+ }
+ if (accept) {
+ price = special[i][n] + lowest_price(n, tmp, prices, special, specialSize,
+ specialColSize);
+ min = fmin(min, price);
+ }
+ }
+ hash_push(need, min);
+ return min;
+}
+
+int shoppingOffers(int *price, int priceSize, int **special, int specialSize,
+ int *specialColSize, int *needs, int needsSize) {
+ int need = 0, ans;
+ hash_init();
+ for (int i = 0; i < needsSize; i++)
+ need |= (needs[i] << (i * 4));
+ ans = lowest_price(priceSize, need, price, special, specialSize,
+ specialColSize);
+ hash_free();
+ return ans;
+}
+
+int main() {
+ int p1[] = {2, 5}, s1i[2][3] = {{3, 0, 5}, {1, 2, 10}}, n1[] = {3, 2};
+ int p2[] = {2, 3, 4}, s2i[2][4] = {{1, 1, 0, 4}, {2, 2, 1, 9}},
+ n2[] = {1, 2, 1};
+ struct two_d_arr s1, s2;
+ two_d_arr_init(&s1, ARRAY_SIZE(s1i), ARRAY_SIZE(s1i[0]), s1i);
+ two_d_arr_init(&s2, ARRAY_SIZE(s2i), ARRAY_SIZE(s2i[0]), s2i);
+ printf("%d\n", shoppingOffers(p1, ARRAY_SIZE(p1), s1.arr, s1.row_size,
+ s1.col_size, n1, ARRAY_SIZE(n1))); // expect: 14
+ printf("%d\n", shoppingOffers(p2, ARRAY_SIZE(p2), s2.arr, s2.row_size,
+ s2.col_size, n2, ARRAY_SIZE(n2))); // expect: 11
+ two_d_arr_free(&s1);
+ two_d_arr_free(&s2);
+}