【leetcode】167. Two Sum II - Input array is sorted

一、题目描述

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

题目解读：一个升序的数组numbers，求出数组中两个数相加为target，返回这两个数的下标

思路：一开始的想法，从头到尾遍历，然后在里面再嵌套一个循环。但是这种方法会超时。看了别人的方法，设置两个指针一个从头往后遍历，一个从后往前遍历。

c++代码（8ms，15.28%）

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

}
};