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

You have to find two non-overlapping sub-arrays of arr each with a sum equal target. There can be multiple answers so you have to find an answer where the sum of the lengths of the two sub-arrays is minimum.

Return the minimum sum of the lengths of the two required sub-arrays, or return -1 if you cannot find such two sub-arrays.

Example 1:

Input: arr = [3,2,2,4,3], target = 3
Output: 2
Explanation: Only two sub-arrays have sum = 3 ([3] and [3]). The sum of their lengths is 2.

Example 2:

Input: arr = [7,3,4,7], target = 7
Output: 2
Explanation: Although we have three non-overlapping sub-arrays of sum = 7 ([7], [3,4] and [7]), but we will choose the first and third sub-arrays as the sum of their lengths is 2.

Example 3:

Input: arr = [4,3,2,6,2,3,4], target = 6
Output: -1
Explanation: We have only one sub-array of sum = 6.

Solution

var minSumOfLengths = function(arr, target) {

const n = arr.length;

const best = new Array(n).fill(Infinity);

const map = new Map();

map.set(0, -1);

let prefix = 0;

let minLen = Infinity;

let ans = Infinity;

for (let i = 0; i < n; i++) {

prefix += arr[i];

if (map.has(prefix - target)) {

const start = map.get(prefix - target);

const len = i - start;

if (start >= 0 && best[start] !== Infinity) {

ans = Math.min(ans, len + best[start]);

}

minLen = Math.min(minLen, len);

}

best[i] = minLen;

map.set(prefix, i);

}

return ans === Infinity ? -1 : ans;

};

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