Leetcode_167. 兩數之和 II - 輸入有序陣列
阿新 • • 發佈:2021-10-03
題目:here
解法:
二分法:
class Solution { public: vector<int> twoSum(vector<int>& numbers, int target) { for (int i = 0; i < numbers.size(); ++i) { int low = i + 1, high = numbers.size() - 1; while (low <= high) { int mid = (high - low) / 2 + low; if (numbers[mid] == target - numbers[i]) { return {i + 1, mid + 1}; } else if (numbers[mid] > target - numbers[i]) { high = mid - 1; } else { low = mid + 1; } } } return {-1, -1}; } };
複雜度分析
- 時間複雜度:nlogn
- 空間複雜度:1
雙指標
class Solution { public: vector<int> twoSum(vector<int>& numbers, int target) { int low = 0, high = numbers.size() - 1; while (low < high) { int sum = numbers[low] + numbers[high]; if (sum == target) { return {low + 1, high + 1}; } else if (sum < target) { ++low; } else { --high; } } return {-1, -1}; } };
複雜度分析
- 時間複雜度:n
- 空間複雜度:1