LeetCode TwoSum题解

题目

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 2 + 7 = 9,return [0, 1].

解题思路：

  利用HashMap来记录数字及对应的下标，用减法来计算判定。

代码如下：

public int[] twoSum(int[] nums, int target) {        int[] result = new int[2];        Map<Integer, Integer> map = new HashMap<Integer, Integer>();        for (int i = 0; i < nums.length; i++) {            if (map.containsKey(target - nums[i])) {                result[1] = i ;                result[0] = map.get(target - nums[i]);                return result;            }            map.put(nums[i], i );       }       return result;}