Tuesday, August 4, 2020

LeetCode [523] Continuous Subarray Sum

Given a list of non-negative numbers and a target integer k, write a function to check if the array has a continuous subarray of size at least 2 that sums up to the multiple of k, that is, sums up to n*k where n is also an integer.

Example 1:
Input: [23, 2, 4, 6, 7],  k=6
Output: True
Explanation: Because [2, 4] is a continuous subarray of size 2 and sums up to 6.
Example 2:
Input: [23, 2, 6, 4, 7],  k=6
Output: True
Explanation: Because [23, 2, 6, 4, 7] is an continuous subarray of size 5 and sums up to 42.

Note:
  1. The length of the array won't exceed 10,000.
  2. You may assume the sum of all the numbers is in the range of a signed 32-bit integer.
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
class Solution {
    public boolean checkSubarraySum(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        map.put(0,-1);
        int s = 0, n = nums.length;
        for(int i=0; i<n; ++i){
            s += nums[i];
            int r = s%k;
            if(map.containsKey(r)){
                int j = map.get(r);
                if(i-j>=2) return true;
            }else{
                map.put(r, i);
            }
        }
        return false;
    }
}

No comments:

Post a Comment