[leetcode 167] Two Sum II - Input array is sorted

Question:

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：

设置两个指针LR,开始时候L=0，R = len-1；将num[L] + num[R] 与target相比较，如果target大，则++L，如果target小，则--R，相等，则返回LR；

代码如下:

<pre name="code" class="cpp"><span style="font-size:14px;">vector<int> twoSum(vector<int> &numbers, int target){
vector<int> ans;
int left = 0, right = numbers.size()-1;
int tmpSum = 0;

while(left < right){
tmpSum = numbers[left] + numbers[right];
if (tmpSum == target){
ans.push_back(left+1);
ans.push_back(right+1);
return ans;
}
else
if (tmpSum > target){
--right;
}else{
++left;
}
}
return ans;
}</span>