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author | jack <[email protected]> | 2024-06-14 13:13:15 -0600 |
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committer | jack <[email protected]> | 2024-06-14 13:13:15 -0600 |
commit | d343a3b18dbaca9297d4f7b2280c4a16f0a5c8aa (patch) | |
tree | 96df922dae2a5073d9a50ea70c7aae6aa37e3ebe /single_element_sorted_arr.c | |
download | leetcode-d343a3b18dbaca9297d4f7b2280c4a16f0a5c8aa.tar.gz leetcode-d343a3b18dbaca9297d4f7b2280c4a16f0a5c8aa.zip |
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Diffstat (limited to 'single_element_sorted_arr.c')
-rw-r--r-- | single_element_sorted_arr.c | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/single_element_sorted_arr.c b/single_element_sorted_arr.c new file mode 100644 index 0000000..f8ecdaa --- /dev/null +++ b/single_element_sorted_arr.c @@ -0,0 +1,51 @@ +// 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 +} |