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test54.java
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46 lines (43 loc) · 1.47 KB
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package byteDance;
import javax.print.attribute.IntegerSyntax;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
/**
* @Author:lizeyang
* @Date:2020/5/23 16:33
* function:给出一个数组nums，一个值k，找出数组中的两个下标 i，j 使得 nums[i] + nums[j] = k.
*/
public class test54 {
//如果数组有重复元素，暴力解决，O(n2)
//如果数组无重复元素，借助辅助空间HashMap,时间复杂度O(n)，额外空间复杂度O(n)
public static List<int[]> test(int[] nums, int k) {
List<int[]> list = new ArrayList<>();
if (nums == null || nums.length == 0) {
return list;
}
HashMap<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
if (!map.containsKey(nums[i])) {
map.put(nums[i], i);
}
if (map.containsKey(k - nums[i])) {
int[] res = new int[2];
res[0] = i;
res[1] = map.get(k - nums[i]);
list.add(res);
map.remove(nums[i]);
map.remove(k - nums[i]);
}
}
return list;
}
public static void main(String[] args) {
int[] nums = {1, 4, 6, 3, 8, 2, 9};
List<int[]> res = test(nums, 10);
for (int i = 0; i < res.size(); i++) {
System.out.println(res.get(i)[0] + " " + res.get(i)[1]);
}
}
}