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-rw-r--r--avoid_flood_city.c85
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diff --git a/avoid_flood_city.c b/avoid_flood_city.c
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+// 1488. Avoid Flood in The City
+#include "leetcode.h"
+
+/*
+ * your country has an infinite number of lakes. initially, all the lakes are
+ * empty. but when it rains over the n'th lake, the n'th lake becomes full of
+ * water. if it rains over a lake that is full of water, there will be a flood.
+ * your goal is to avoid any floods. if there are multiple valid answers, return
+ * any of them. if it is impossible to avoid flood, return an empty array.
+ * notice that if yo uchose to dry a full lake, it becomes empty. but if you
+ * chose to dry an empty lake, nothing happens.
+ */
+
+int *avoidFlood(int *rains, int rainsSize, int *returnSize) {
+ *returnSize = rainsSize;
+ int s_idx = 0, top = 0, n = 2 * rainsSize;
+ int *ans = (int *)calloc(rainsSize, sizeof(int));
+ int *stack = (int *)malloc(rainsSize * sizeof(int));
+ int **hash = (int **)calloc(n, sizeof(int *));
+ for (int i = 0; i < rainsSize; i++) {
+ if (!rains[i]) {
+ stack[s_idx] = i;
+ s_idx++;
+ ans[i] = 1;
+ } else {
+ ans[i] = -1;
+ int val = rains[i], d = val;
+ while (1) {
+ if (!hash[d % n]) {
+ hash[d % n] = (int *)malloc(2 * sizeof(int));
+ hash[d % n][0] = val;
+ hash[d % n][1] = i;
+ break;
+ } else if (hash[d % n][0] == val) {
+ if (top == s_idx) {
+ *returnSize = 0;
+ goto exit;
+ }
+ for (int j = top; j < s_idx; i++) {
+ if (stack[j] > hash[d % n][1]) {
+ ans[stack[j]] = val;
+ stack[j] = -1;
+ hash[d % n][1] = i;
+ break;
+ }
+ if (j == s_idx - 1) {
+ *returnSize = 0;
+ goto exit;
+ }
+ }
+ break;
+ } else
+ d++;
+ }
+ while (top < s_idx && stack[top] == -1)
+ top++;
+ }
+ }
+exit:
+ free(stack);
+ for (int i = 0; i < n; i++)
+ if (hash[i])
+ free(hash[i]);
+ free(hash);
+ return ans;
+}
+
+int main() {
+ int r1[] = {1, 2, 3, 4}, r2[] = {1, 2, 0, 0, 2, 1}, r3[] = {1, 2, 0, 1, 2};
+ int rs1, *af1 = avoidFlood(r1, ARRAY_SIZE(r1), &rs1);
+ int rs2, *af2 = avoidFlood(r2, ARRAY_SIZE(r2), &rs2);
+ int rs3, *af3 = avoidFlood(r3, ARRAY_SIZE(r3), &rs3);
+ for (int i = 0; i < rs1; i++)
+ printf("%d ", af1[i]); // expect: -1 -1 -1 -1
+ printf("\n");
+ for (int i = 0; i < rs2; i++)
+ printf("%d ", af2[i]); // expect: -1 -1 2 1 -1 -1
+ printf("\n");
+ for (int i = 0; i < rs3; i++)
+ printf("%d ", af3[i]); // expect: null
+ printf("\n");
+ free(af1);
+ free(af2);
+ free(af3);
+}