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authorjack <[email protected]>2024-06-14 13:13:15 -0600
committerjack <[email protected]>2024-06-14 13:13:15 -0600
commitd343a3b18dbaca9297d4f7b2280c4a16f0a5c8aa (patch)
tree96df922dae2a5073d9a50ea70c7aae6aa37e3ebe /single_element_sorted_arr.c
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+// 540. Single Element in a Sorted Array
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/*
+ * given a sorted array consisting of only integers where very element appears
+ * exactly twice, except for one element which appears exactly once. return the
+ * single element that appears only once. solution func must be o(ln) time and
+ * o(1) space complexity.
+ */
+
+int singleNonDuplicate(int *nums, int nums_size) {
+ if (nums_size == 1)
+ return nums[0];
+ if (nums[0] != nums[1])
+ return nums[0];
+ if (nums[nums_size - 1] != nums[nums_size - 2])
+ return nums[nums_size - 1];
+ int left = 2, right = nums_size - 3, mid;
+ bool ptr_l, ptr_r;
+ while (left < right) {
+ mid = (left + right) / 2;
+ ptr_l = (nums[mid] == nums[mid - 1]) ? true : false;
+ ptr_r = (nums[mid] == nums[mid + 1]) ? true : false;
+ // if ((ptr_l == false) && (ptr_r == false))
+ if (!ptr_l && !ptr_r)
+ return nums[mid];
+ if (mid % 2 == 0) {
+ if (ptr_l)
+ right = mid - 2;
+ else
+ left = mid + 2;
+ } else {
+ if (ptr_r)
+ right = mid - 1;
+ else
+ left = mid + 1;
+ }
+ }
+ if (nums[left] != nums[left - 1] || nums[left] != nums[left + 1])
+ return nums[left];
+ else
+ return nums[right];
+}
+
+int main() {
+ int nums1[] = {1, 1, 2, 3, 3, 4, 4, 8, 8}, nums2[] = {3, 3, 7, 7, 10, 11, 11};
+ printf("%d\n", singleNonDuplicate(nums1, 9)); // expect: 2
+ printf("%d\n", singleNonDuplicate(nums2, 9)); // expect: 10
+}