1. Two Sum
难度: Easy
刷题内容
原题连接
- https://leetcode.com/problems/two-sum
内容描述
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].
解题方案
思路 1 **- 时间复杂度: O(N)*- 空间复杂度: O(N)***
class Solution {
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> lookup = new HashMap<>();
int[] res = new int[2];
for (int i = 0; i < nums.length; i++) {
if (lookup.containsKey(target - nums[i])) {
res = new int[] { lookup.get(target - nums[i]), i };
break;
} else {
lookup.put(nums[i], i);
}
}
return res;
}
}
