练习笔记供自己查找方便,有人有更好的解法,一起交流学习哈~~~~
package pratice.leetcode; import java.util.*; public class problem1 { //复杂度O(n^2) public static int[] twoSum(int[] nums, int target) { int[] result=new int[2]; for(int i=0;i<nums.length;i++){ result[0]=i; int flag=0; for(int j=i+1;j<nums.length;j++){ if(nums[i]+nums[j]==target){ result[1]=j; flag=1; break; } } if(flag==1){ break; } } return result; } //Two-pass Hash Table 复杂度O(n) public static int[] twoSum1(int[] nums,int target){ Map<Integer,Integer> map=new HashMap<>(); for(int i=0;i<nums.length;i++){ map.put(nums[i], i); } for(int i=0;i<nums.length;i++){ int complement=target-nums[i]; if(map.containsKey(complement)&&map.get(complement)!=i){ return new int[]{i,map.get(complement)}; } } throw new IllegalArgumentException("No two sum solution!"); } public static void main(String[] args){ int[] nums={2,7,11,15}; int[] result=twoSum1(nums,17); System.out.println("["+result[0]+","+result[1]+"]"); } }