README_EN.md

1. Two Sum

中文文档

Description

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

You can return the answer in any order.

 

Example 1:

Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].

Example 2:

Input: nums = [3,2,4], target = 6
Output: [1,2]

Example 3:

Input: nums = [3,3], target = 6
Output: [0,1]

 

Constraints:

• 2 <= nums.length <= 103
• -109 <= nums[i] <= 109
• -109 <= target <= 109
• Only one valid answer exists.

Solutions

Python3

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        helper = {}
        for i, v in enumerate(nums):
            num = target - v
            if num in helper:
                return [helper[num], i]
            helper[v] = i

Java

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

C++

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        unordered_map<int, int> map;
        for (int i = 0; i < nums.size(); ++i) {
            int num = target - nums[i];
            if (map.find(num) != map.end()) {
                return {map[num], i};
            }
            map[nums[i]] = i;
        }
        return {};
    }
};

Go

func twoSum(nums []int, target int) []int {
	numMap := make(map[int]int)
	for i, num := range nums {
		other := target - num
		if _, ok := numMap[other]; ok {
			return []int{numMap[other], i}
		}
		numMap[num] = i
	}
	return nil
}

JavaScript

var twoSum = function (nums, target) {
  const map = new Map();
  for (let i = 0; i < nums.length; i++) {
    if (map.has(target - nums[i])) {
      return [map.get(target - nums[i]), i];
    }
    map.set(nums[i], i);
  }
  return [];
};

Swift

class Solution {
    func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
        var map = [Int: Int]()
        var i = 0
        for num in nums {
            map[num] = i
            i = i + 1
        }
        i = 0
        for num in nums {
            if let otherIndex = map[target - num], otherIndex != i {
                return [i, otherIndex]
            }
            i = i + 1
        }
        return []
    }
}

Nim

import std/enumerate

proc twoSum(nums: seq[int], target: int): seq[int] =
    var
        bal: int
        tdx: int
    for idx, val in enumerate(nums):
        bal = target - val
        if bal in nums:
            tdx = nums.find(bal)
            if idx != tdx:
                return @[idx, tdx]

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