Given an array of integers and an integer k, you need to find the minimum size of continuous subarrays whose sum equals to k, and return its length.
if there are no such subarray, return -1.
Example
Example1
Input: nums = [1,1,1,2] and k = 3
Output: 2
Example2
Input: nums = [2,1,-1,4,2,-3] and k = 3
Output: 2
Notice
the integer nums[i] may lower than 0
Solution 1: O(N^2) TLE
public class Solution { /** * @param nums: a list of integer * @param k: an integer * @return: return an integer, denote the minimum length of continuous subarrays whose sum equals to k */ public int subarraySumEqualsKII(int[] nums, int k) { // write your code here int[] prefix = new int[nums.length]; for (int i = 0; i < nums.length; i++) { if (i == 0) { prefix[i] = nums[i]; continue; } prefix[i] = prefix[i - 1] + nums[i]; } System.out.println(Arrays.toString(prefix)); int res = Integer.MAX_VALUE; for (int i = 0; i < nums.length; i++) { for (int j = i; j < nums.length; j++) { if (i == 0) { if (prefix[j] == k) { res = Math.min(res, j + 1); } continue; } if (prefix[j] - prefix[i - 1] == k) { res = Math.min(res, j - i + 1); } } } return res == Integer.MAX_VALUE ? -1 : res; } }
Solution 2:
public class Solution { /** * @param nums: a list of integer * @param k: an integer * @return: return an integer, denote the minimum length of continuous subarrays whose sum equals to k */ public int subarraySumEqualsKII(int[] nums, int k) { // write your code here Map<Integer, Integer> map = new HashMap<>(); int sum = 0; int res = Integer.MAX_VALUE; map.put(0, -1); for (int i = 0; i < nums.length; i++) { sum += nums[i]; if (map.containsKey(sum - k)) { // actually get the i - 1 index for map.get(sum - k) res = Math.min(res, i - map.get(sum - k)); } map.put(sum, i); } return res == Integer.MAX_VALUE ? -1 : res; } }
原文地址:https://www.cnblogs.com/xuanlu/p/12515155.html
时间: 2024-11-05 15:57:46