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  • LeetCode 1 Two Sum

    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].


    暴力解法(Java):

    1 class Solution {
    2     public int[] twoSum(int[] nums, int target) {
    3         for(int i=0;i<nums.length;i++)
    4             for(int j=i+1;j<nums.length;j++)
    5                 if(nums[i]+nums[j]==target)
    6                     return new int[]{i,j};
    7         return new int[]{0,0};
    8     }
    9 }

    利用hashset,遍历nums,若在set中找到一个值与当前值相加为target,则返回两个下标,否则将当前值加入set(Java):

    class Solution {
        public int[] twoSum(int[] nums, int target) {
            
            Set<Integer> set = new HashSet<>();
            int i=0;
            int j=0;
            
            for(i=0;i<nums.length;i++)
            {
                if(set.contains(target-nums[i])) 
                    break;
                else
                    set.add(nums[i]);
            }
            
            while(nums[j]!=target-nums[i])
                j++;
            
            return new int[]{j,i};
        }
    }
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  • 原文地址:https://www.cnblogs.com/trymorel/p/12520917.html
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