1.两数之和

leetcode链接：
https://leetcode.cn/problems/two-sum/

方案一：暴力枚举

自行做出

for (int i = 0; i < nums.length -1; i++) {
	for (int j = i+1; j < nums.length; j++) {
		if (nums[i] + nums[j] == target)
			return new int[]{i,j};
	}
}
return nums;

结果

解答成功:
执行耗时:58 ms,击败了14.31% 的Java用户
内存消耗:42.4 MB,击败了32.18% 的Java用户

方案二：哈希表

https://leetcode.cn/problems/two-sum/solution/liang-shu-zhi-he-by-leetcode-solution/

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

作者：LeetCode-Solution
链接：https://leetcode.cn/problems/two-sum/solution/liang-shu-zhi-he-by-leetcode-solution/
来源：力扣（LeetCode）
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