解决两数之和 (Javascript, Java, C#, Swift, Kotlin, Python,C++, Golang)
给定一个整数数组，返回两个数字的索引，以便它们加起来成为一个特定的目标。
您可以假定每个输入都只有一个解决方案，并且您可能不会两次使用同一元素。
举例:
给定数组 =[2, 7, 11, 15], 目标值 = 9,
因为nums[0]+ nums[1] = 2 + 7 = 9,
所以返回 [0,1].
思路:
我们定义一个字典来存储元素及其索引。
我们将一一检查元素。
假设当前元素是a;
我们将元素及其索引存储到字典中；
并使用目标减去当前元素来获得差值b；
我们检查映射是否可以使用b作为键来获取任何内容，如果该值不为空并且其索引也不相同，则得到答案。
Javascript:
twoSum =(nums, target)=> {
let map = newMap;
for(let i = 0; i< nums.length; i ++) {
let a = nums[i];
let b = target - a;
let j = map.get(b);
if(j !== undefined) {
if(j !== i){
return [i, j ];
}
}
map.set(a, i);
}
return [];
}
console.log(twoSum([2,7,11,15],9))
console.log(twoSum([3,2,4],6))
console.log(twoSum([3,3],6))
Java:
importjava.util.*;
public classHelloWorld{
publicstatic void main(String []args){
System.out.println(Arrays.toString(twoSum(newint[]{2,7,11,15}, 9)));
System.out.println(Arrays.toString(twoSum(newint[]{3,2,4}, 6)));
System.out.println(Arrays.toString(twoSum(newint[]{3,3}, 6)));
}
public static int[] twoSum(int[] nums, inttarget) {
Map<Integer,Integer> map = new HashMap<Integer, Integer>();
for(int i = 0 ; i<nums.length; i++){
int a = nums[i];
int b = target - a;
Integer j = map.get(b);
map.put(a, i);
if(j != null && i != j) {
return new int[]{i,j};
}
}
return new int[]{};
}
}
c#:
usingSystem;
usingSystem.Collections.Generic;
classHelloWorld {
public staticvoid Main(string[] args)
{
Console.WriteLine(string.Join(",",twoSum(newint[]{2,7,11,15}, 9)));
Console.WriteLine(string.Join(",",twoSum(new int[]{3,2,4},6)));
Console.WriteLine(string.Join(",",twoSum(new int[]{3,3},6)));
}
public staticint[] twoSum(int[] nums, inttarget) {
Dictionary<int,int> map= new Dictionary<int, int>();
for(inti = 0 ; i<nums.Length; i++) {
int a = nums[i];
int b = target - a;
if(map.ContainsKey(b)) {
int j = map[b];
if(i != j) {
return new int[]{i,j};
}
}
map[a] = i;
}
returnnew int[]{};
}
}
Swift:
importFoundation
functwoSum(_ nums: [Int], _ target:Int) -> [Int] {
var map = [Int :Int]()
for (i, a) innums.enumerated() {
var b = target - a;
var j = map[b]
if(j != nil) {
var jj = j!
return [i,jj]
}
map[a] = i
}
return []
}
print(twoSum([2,7,11,15],9))
print(twoSum([3,2,4],6))
print(twoSum([3,3],6))
Kotlin:
funtwoSum(nums: IntArray, target:Int): IntArray {
valmap:HashMap<Int,Int> =HashMap<Int,Int>()
for ((i, a) innums.withIndex()) {
varb = target - a
var j = map.get(b)
if(j != null) {
var jj = j!!
if(jj != i){
return intArrayOf(i, j)
}
}
map.set(a, i)
}
returnintArrayOf()
}
fun main() {
println(twoSum(intArrayOf(2,7,11,15),9).joinToString(","))
println(twoSum(intArrayOf(3,2,4),6).joinToString(","))
println(twoSum(intArrayOf(3,3),6).joinToString(","))
}
Python:
deftwoSum(nums, target):
map = {}
i = 0
l = len(nums)
while i < l:
a = nums[i]
b = target - a
j = map.get(b)
if j is not None:
if j != i:
return [i,j]
map[a] = i
i += 1
return[]
print(twoSum([2,7,11,15],9))
print(twoSum([3,2,4],6))
print(twoSum([3,3],6))
C++:
#include<iostream>
#include<vector>
#include<map>
usingnamespace std;
vector<int>twoSum(vector<int>&nums, int target) {
std:map<int,int> map;
vector<int>ret;
for(int i = 0; i< nums.size(); i ++) {
int a = nums[i];
int b = target - a;
std::map<int,int>::iterator it =map.find(b);
if(it != map.end()) {
int j = it->second;
if(j != i) {
ret.push_back(i);
ret.push_back(j);
return ret;
}
}
map.insert(std::pair<int, int>(a,i));
}
return ret;
}
int main()
{
{
std::vector<int> nums;
nums.push_back(2);
nums.push_back(7);
nums.push_back(11);
nums.push_back(15);
std::vector<int> ret =twoSum(nums, 9);
for (std::vector<int>::iteratorit = ret.begin() ; it != ret.end(); ++it){
std::cout << *it <<',';
}
std::cout << '\n';
}
{
std::vector<int> nums;
nums.push_back(3);
nums.push_back(2);
nums.push_back(4);
std::vector<int> ret =twoSum(nums, 6);
for (std::vector<int>::iteratorit = ret.begin() ; it != ret.end(); ++it){
std::cout << *it <<',';
}
std::cout << '\n';
}
{
std::vector<int> nums;
nums.push_back(3);
nums.push_back(3);
std::vector<int> ret =twoSum(nums, 6);
for (std::vector<int>::iteratorit = ret.begin() ; it != ret.end(); ++it){
std::cout << *it <<',';
}
std::cout << '\n';
}
return 0;
}
Golang:
package main
import (
"fmt"
)
functwoSum(nums []int, target int)[]int {
var mapCheck = make(map[int]int)
var a int
var b int
for i:=0; i < len(nums) ; i ++ {
a = nums[i]
b = target - a
if j, ok := mapCheck[b]; ok {
if( j != i){
return[]int{i,j}
}
}
mapCheck [a] = i
}
return []int{}
}
func main(){
fmt.Println(twoSum([]int{2,7,11,15},9))
fmt.Println(twoSum([]int{3,2,4}, 6))
fmt.Println(twoSum([]int{3,3}, 6))
}
