两数之和 (twoSum)

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

---

解法思路

用 target 挨个 减去 nums 中的项，然后得出结果，如果结果 nums 中存在，则记录下标

Golang

package main

import (
	"fmt"
)

func main() {
	nums := []int{
		3, 2, 4,
	}
	target := 6

	results := twoSum(nums, target)
	fmt.Println("results", results)

	results2 := twoSum2(nums, target)
	fmt.Println("results2", results2)
}

// 暴力求解
func twoSum(nums []int, target int) []int {
	returnVal := []int{}
	for k1, v1 := range nums {
		diff := target - v1
		for k2, v2 := range nums {
			if diff == v2 && k2 != k1 {
				returnVal = append(returnVal, k2)
			}
		}
	}
	return returnVal
}

// 利用哈希 map
func twoSum2(nums []int, target int) []int {
	hashTable := map[int]int{}
	for i, x := range nums {
		p, ok := hashTable[target-x]
		if ok {
			return []int{p, i}
		}
		hashTable[x] = i
	}
	return nil
}

JavaScript

// 暴力求解
var twoSum = function (nums, target) {
  for (let i = 0; i < nums.length; i++) {
    const el = nums[i];
    const diff = target - el;
    const idxOf = nums.indexOf(diff);
    if (idxOf > -1 && idxOf != i) {
      return [i, idxOf];
    }
  }
  return;
};

// 利用哈希map
var twoSum2 = function (nums, target) {
  var map = {};
  for (let i = 0; i < nums.length; i++) {
    const el = nums[i];
    const res = map[target - el];
    if (res !== undefined) {
      return [res, i];
    }
    map[el] = i;
  }
  return;
};

// 代码执行块
(function () {
  const nums = [2, 7, 11, 15];
  const target = 9;
  // const result = twoSum(nums, target);
  // console.log('result', result);

  const result2 = twoSum2(nums, target);
  console.log('result2', result2);
})();