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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
}
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