LeetCode167—Two Sum II - Input array is sorted

原题

原题链接

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.

Input: numbers={2, 7, 11, 15}, target=9

Output: index1=1, index2=2

分析

在已经

sorted

过的

vector

中找到两个数相加为给定目标。

一个办法是：

1.指定两个索引分别指向数组的头和尾（最小和最大部分）。

2.两个索引所指的数相加，如果相等，直接返回结果。

3.如果相加结果大于目标，则把右边索引向左移动一格。

4.如果相加结果小于目标，则把左边索引向右移动一格。

class Solution {
public:
vector<int> twoSum(vector<int>& numbers, int target) {
vector<int> res;
int l=0;
int r=numbers.size()-1;
while(l<r)
{
int tmp = numbers[l]+numbers[r];
if(tmp == target)
{
res.push_back(l+1);
res.push_back(r+1);
break;
}
else if(tmp > target)
--r;
else
++l;
}
return res;
}
};