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+// 540. Single Element in a Sorted Array
+#include "leetcode.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.
+ */
+
+class Solution {
+public:
+ int singleNonDuplicate(vector<int> &nums) {
+ int low = 0, high = nums.size() - 1, mid;
+ while (low < high) {
+ mid = (low + high) / 2;
+ if ((mid % 2 && nums[mid - 1] == nums[mid]) ||
+ (!(mid % 2) && nums[mid] == nums[mid + 1]))
+ low = mid + 1;
+ else
+ high = mid;
+ }
+ return nums[low];
+ }
+};
+
+int main() {
+ Solution obj;
+ vector<int> nums1 = {1, 1, 2, 3, 3, 4, 4, 8, 8},
+ nums2 = {3, 3, 7, 7, 10, 11, 11};
+ cout << obj.singleNonDuplicate(nums1) << endl; // expect: 2
+ cout << obj.singleNonDuplicate(nums2) << endl; // expect: 10
+}