Leetcode 167. Two Sum II - Input array is sorted-优快云博客

本文链接：https://blog.youkuaiyun.com/Quincuntial/article/details/86715705

本文深入探讨了两数之和问题的两种解决方案，一种是通过双重循环遍历，另一种则利用二分查找提高效率。文章详细展示了算法的实现代码，并对比了不同版本的优劣。

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文章作者：Tyan
博客：noahsnail.com | 优快云 | 简书

1. Description

Two Sum II - Input array is sorted

2. Solution

Version 1

class Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
    	int size = numbers.size();
    	vector<int> result;
        for(int i = 0; i < size - 1; i++) {
        	for(int j = i + 1; j < size; j++) {
        		if(numbers[i] + numbers[j] == target) {
        			result.push_back(i + 1);
        			result.push_back(j + 1);
        			return result;
        		}
        	}
        }
        return result;
    }
};

Version 2

class Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
    	int size = numbers.size();
    	vector<int> result;
        for(int i = 0; i < size - 1; i++) {
        	int other = binarySearch(numbers, i + 1, size - 1, target - numbers[i]);
        	if(other != - 1) {
        		result.push_back(i + 1);
        		result.push_back(other + 1);
        		return result;
        	}
        }
        return result;
    }

private:
    int binarySearch(vector<int>& numbers, int left, int right, int target) {
    	while(left <= right) {
    		int middle = (left + right) / 2;
    		if(numbers[middle] == target) {
    			return middle;
    		}
    		else if(numbers[middle] > target) {
    			right = middle - 1;
    		}
    		else {
    			left = middle + 1;
    		}
    	}
    	return -1;
    }
};