[勇者闯LeetCode] 167. Two Sum II

[勇者闯LeetCode] 167. Two Sum II - Input array is sorted

Description

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution and you may not use the same element twice.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

Information

• Tags: Array | Two Pointers | Binary Search
• Difficulty: Easy

Solution

使用两个指针left和right从numbers两端往中间扫描，当两端之和等于target时，返回坐标，若两端之和小于target则left向右移，若两端之和大于target则right往左移。

C++ Code

class Solution {public:    vector<int> twoSum(vector<int>& numbers, int target) {        int left = 0, right = numbers.size()-1;        while (left != right) {            const auto sum = numbers[left] + numbers[right];            if (sum < target) {                ++left;            } else if (sum > target) {                --right;            }            else {                return {left+1, right+1};            }        }        return {0, 0};    }};