LeetCode笔记：1. Two Sum

Question: （谷歌翻译）

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，返回两个数字的索引，使得它们相加到一个特定的目标。

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只有一个解决方案，您不能使用相同的元素两次。

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,

return [0, 1].

Top Solutions:

该解法**。

public class Solution {
public int[] twoSum(int[] nums, int target) {
int num1;
int[] result = new int[2];

for (int i = 0; i < nums.length; i++) {
num1 = target - nums[i];
for (int j = i + 1; j < nums.length; j++) {
if (num1 == nums[j]) {
result[0] = i;
result[1] = j;
}
}
}

return result;
}
}

“Accepted Java O(n) Solution”

https://discuss.leetcode.com/topic/2447/accepted-java-o-n-solution

My Solution:

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