Leetcode-001-两数之和

本题思路是用一个key-value数据结构去保存已经遍历到的数字。

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

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        demo = dict()
        for idx, i in enumerate(nums):
            if target - i in demo:
                return [idx, demo[target-i]]
            else:
                demo[i] = idx