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1. Two Sum

1. Two Sum

作者: 丶沧月 | 来源:发表于2019-03-06 17:52 被阅读0次

    题目描述

    Given an array of integers, return indices of the two numbers such that they add up to a specific target.
    给定一个整数数组,返回两个数字的指数,使它们相加到特定目标。
    You may assume that each input would have exactly one solution, and you may not use the same element twice.
    您可以假设每个输入都具有完全一个解决方案,并且您可能不会使用* same *元素两次。

    Example:

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

    思路与实现

    使用 Map ,O(n) 时间复杂度

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

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