[LeetCode]167. Two Sum II - Input array is sorted 解题报告(C++)
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.
Note:
- 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.
Example:
Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.
题目大意
- 给定一个
sorted
的数组. 找到 和为target
的两数的坐标索引.
解题思路
方法1:
- 由于数组已经排序了. 从左右两边开始搜索.
- 若左右和大于 target. 说明右边太大. j–
- 若左右和小于target. 说明左边太小. i++
- 直至相等.返回 {i,j}
代码实现:
class Solution0{
public:
vector<int> twoSum(vector<int>& numbers, int target) {
int size = numbers.size();
int i, j;
i = 0; j = size - 1;
while (i < j) {
int sum = numbers[i] + numbers[j];
if (sum> target) {
j--;
}
else if (sum < target){
i++;
}
else {
return{ i+1,j+1 };
}
}
return{};
}
};
小结
- easy!