标签：length leetcode 一个 个数 list add odi get twosum rom
This problem was recently asked by Google.
Given a list of numbers and a number k, return whether any two numbers from the list add up to k.
For example, given [10, 15, 3, 7] and k of 17, return true since 10 + 7 is 17.
Bonus: Can you do this in one pass?
经典2-sum问题的变形. 最直观的做法是first pass, 用HashMap保存每个数和其index的mapping关系， 然后second pass来寻找是否有满足要求的。 需要注意的一点是，同一个位置的数字不能使用两次.
1 public class Solution { 2 public int[] twoSum(int[] nums, int target) { 3 Map<Integer, Integer> hm = new HashMap<Integer, Integer>(); 4 for(int i = 0; i < nums.length; i++) 5 { 6 hm.put(nums[i], i); 7 } 8 9 for(int i = 0; i < nums.length; i++) 10 { 11 if(hm.containsKey(target - nums[i]) && i != hm.get(target - nums[i])) 12 { 13 int[] r = new int[2]; 14 r[0] = i; 15 r[1] = hm.get(target - nums[i]); 16 return r; 17 } 18 } 19 return null; 20 } 21 }
1 pass solution 就是一边扫描数组， 一边更新Map。 如果找到满足要求的pair， 直接返回， 否则把当前的数插入到Map中.
1 public class Solution { 2 public int[] twoSum(int[] nums, int target) { 3 Map<Integer, Integer> map = new HashMap<Integer, Integer>(); 4 for(int i = 0; i < nums.length; i++) { 5 if(map.containsKey(target - nums[i])) { 6 int[] r = new int[2]; 7 r[0] = map.get(target - nums[i]); 8 r[1] = i; 9 return r; 10 } 11 else { 12 map.put(nums[i], i); 13 } 14 } 15 return null; 16 } 17 }
[Daily Coding Problem] 1 (LeetCode 1). Find if two numbers in an array add up to k
标签：length leetcode 一个 个数 list add odi get twosum rom
原文地址：https://www.cnblogs.com/lz87/p/10106326.html
