Given an array nums and an integer target.
Return the maximum number of non-empty non-overlapping subarrays such that the sum of values in each subarray is equal to target.
Example 1:
Input: nums = [1,1,1,1,1], target = 2
Output: 2
Explanation: There are 2 non-overlapping subarrays [1,1,1,1,1] with sum equals to target(2).
Example 2:
Input: nums = [-1,3,5,1,4,2,-9], target = 6
Output: 2
Explanation: There are 3 subarrays with sum equal to 6.
([5,1], [4,2], [3,5,1,4,2,-9]) but only the first 2 are non-overlapping.
Example 3:
Input: nums = [-2,6,6,3,5,4,1,2,8], target = 10
Output: 3
Example 4:
Input: nums = [0,0,0], target = 0
Output: 3
Constraints:
- 1 <= nums.length <= 10^5
- -10^4 <= nums[i] <= 10^4
- 0 <= target <= 10^6
Solution
class Solution {
public int maxNonOverlapping(int[] nums, int target) {
Map<Integer, Integer> prefixMap = new HashMap<>();
int count = 0;
int sum = 0;
int lastIndex = -1;
prefixMap.put(0, -1);
for (int i = 0; i < nums.length; i++) {
sum+= nums[i];
int remain = sum - target;
if (prefixMap.containsKey(remain)) {
int start = prefixMap.get(remain);
if (start >= lastIndex) {
count++;
lastIndex = i;
}
}
prefixMap.put(sum, i);
}
return count;
}
}