Create: 0034-find-first-and-last-position-of-element-in-sorted-array.cpp

cpp/0034-find-first-and-last-position-of-element-in-sorted-array.cpp

@@ -0,0 +1,32 @@
+/*
+ Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value.
+ Ex. nums = [5,7,7,8,8,10], target = 8 -> [3, 4] (start position is 3, end position is 4)
+
+ Use binary search, firstly binary search left endpoint, then binary search right endpoint.
+
+ Time: O(log n)
+ Space: O(1)
+*/
+
+class Solution {
+public:
+ vector<int> searchRange(vector<int>& nums, int target) {
+ if (nums.empty()) return {-1, -1};
+ int l = 0, r = nums.size() - 1;
+ while (l < r) {
+ int mid = l + r >> 1;
+ if (nums[mid] >= target) r = mid;
+ else l = mid + 1;
+ }
+ if (nums[l] != target) return {-1, -1};
+ int left = l;
+
+ l = 0, r = nums.size() - 1;
+ while (l < r) {
+ int mid = l + r + 1ll >> 1;
+ if (nums[mid] <= target) l = mid;
+ else r = mid - 1;
+ }
+ return {left, r};
+ }
+};