LeetCode 1477: Find Two Non-overlapping Sub-arrays Each With Target Sum Solution

Master LeetCode problem 1477 (Find Two Non-overlapping Sub-arrays Each With Target Sum), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1477. Find Two Non-overlapping Sub-arrays Each With Target Sum

Medium

Array Hash Table Binary Search Dynamic Programming Sliding Window

Problem Explanation

Explanation:

To solve this problem, we can use a two-pointer technique combined with prefix sums. We iterate through the array and calculate the prefix sum at each index. Then, we iterate through the array again and for each index, we find the length of the subarray with sum equal to the target from the left end. We store these lengths in an array.

Next, we iterate through the array in reverse and for each index, we find the length of the subarray with sum equal to the target from the right end. We store these lengths in another array.

Finally, we iterate through both arrays and find the minimum sum of lengths of the two non-overlapping subarrays with the target sum.

Solution Code

class Solution {
    public int minSumOfLengths(int[] arr, int target) {
        int n = arr.length;
        int[] leftSum = new int[n];
        Map<Integer, Integer> map = new HashMap<>();
        map.put(0, -1);
        int sum = 0, minLen = Integer.MAX_VALUE, result = Integer.MAX_VALUE;
        
        for (int i = 0; i < n; i++) {
            sum += arr[i];
            leftSum[i] = minLen;
            if (map.containsKey(sum - target)) {
                int len = i - map.get(sum - target);
                minLen = Math.min(minLen, len);
            }
            map.put(sum, i);
        }
        
        map.clear();
        map.put(0, n);
        sum = 0;
        
        for (int i = n - 1; i >= 0; i--) {
            sum += arr[i];
            if (map.containsKey(sum - target)) {
                int len = map.get(sum - target) - i;
                if (len + leftSum[i] < result) {
                    result = len + leftSum[i];
                }
            }
            if (i > 0) {
                map.put(sum, i);
            }
        }
        
        return result == Integer.MAX_VALUE ? -1 : result;
    }
}

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