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Rotated.cpp
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Rotated.cpp
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class Solution {
public:
bool search(vector<int>& nums, int target) {
int n = nums.size();
if (n == 0) return false;
int end = n - 1;
int start = 0;
while (start <= end) {
int mid = start + (end - start) / 2;
if (nums[mid] == target) {
return true;
}
if (!isBinarySearchHelpful(nums, start, nums[mid])) {
start++;
continue;
}
// which array does pivot belong to.
bool pivotArray = existsInFirst(nums, start, nums[mid]);
// which array does target belong to.
bool targetArray = existsInFirst(nums, start, target);
if (pivotArray ^ targetArray) { // If pivot and target exist in different sorted arrays, recall that xor is true only when both the operands are distinct
if (pivotArray) {
start = mid + 1; // pivot in the first, target in the second
} else {
end = mid - 1; // target in the first, pivot in the second
}
} else { // If pivot and target exist in same sorted array
if (nums[mid] < target) {
start = mid + 1;
} else {
end = mid - 1;
}
}
}
return false;
}
// returns true if we can reduce the search space in current binary search space
bool isBinarySearchHelpful(vector<int>& nums, int start, int element) {
return nums[start] != element;
}
// returns true if element exists in first array, false if it exists in second
bool existsInFirst(vector<int>& nums, int start, int element) {
return nums[start] <= element;
}
};