【Leetcode】Two Sum

题目链接：https://leetcode.com/problems/two-sum/

题目：

Given an array of integers, 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:

思路：

用HashMap保存index1和值，如果剩余数组有target-nums[i],则返回

算法：

public int[] twoSum(int[] nums, int target) {
		Map<Integer, Integer> maps = new HashMap<Integer, Integer>();
		for (int i = 0; i < nums.length; i++) {
			if (maps.containsKey(target - nums[i])) {
				int r1 = maps.get(target - nums[i]) + 1;
				int r2 = i + 1;
				return new int[] { r1, r2 };
			}
			maps.put(nums[i], i);
		}
		return null;
	}