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.
Given nums =[2, 7, 11, 15], target = 9,
Becausenums[0] + nums[1] = 2 + 7 = 9,
return [0,1].
We define a map to store the element with its index as a map;
We are going to check element one by one;
Let's say the current element is a;
We store the element with its index into map;
and use the target to minus the current element to get the difference as b;
We check if the map can get anything with b as the key, if the value is not empty and is also not the same with its index, we get the answer.
twoSum =(nums, target)=> {
let map = new Map;
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))
importjava.util.*;
public classHelloWorld{
public static void main(String []args){
System.out.println(Arrays.toString(twoSum(new int[]{2,7,11,15}, 9)));
System.out.println(Arrays.toString(twoSum(new int[]{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[]{};
}
}
usingSystem;
usingSystem.Collections.Generic;
classHelloWorld {
public static void 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 static int[] 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[]{};
}
}
importFoundation
functwoSum(_ nums: [Int], _ target: Int) -> [Int] {
var map = [Int : Int]()
for (i, a) in nums.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))
funtwoSum(nums: IntArray, target: Int): IntArray {
val map:HashMap<Int,Int> =HashMap<Int,Int>()
for ((i, a) in nums.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)
}
return intArrayOf()
}
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(","))
}
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))
#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;
}
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))
}
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查看原文：Solve two sum problem (Javascript, Java, C#, Swift, Kotlin, Python, C++, Golang)
