两数相和

package com.cjh.leetcode;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Scanner;

import java.util.*;


public class A1 {
	public static void main(String[] args) {
		int[] nums = {2,7,11,15};
		int target = 18;
		System.out.println(Arrays.toString(twoSum1(nums, target)));
	}
	public static int[] twoSum(int[] nums, int target) {
		for (int i = 0; i < nums.length - 1; i++) {
			for (int j = i + 1; j < nums.length; j++) {
				if (nums[i] + nums[j] == target) {
					return new int[]{i,j};
				}
			}
		}
		return new int[]{-1};
	}
	public static int[] twoSum1(int[] nums, int target) {
		Map<Integer, Integer> map = new HashMap();
		for (int i = 0; i < nums.length; i++) {
				if (map.containsKey(target - nums[i])) {
					return new int[]{map.get(target - nums[i]),i};
				}
				map.put(nums[i], i);
			}
		return new int[]{-1};
		}
		
	}