Maximum Number of Ways to Partition an Array LeetCode solution in JavaScript

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/**
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 * @param {number[]} nums
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 * @param {number} k
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 * @return {number}
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 */
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var waysToPartition = function (nums, k) {
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  let totalSum = nums.reduce((acc, curr) => acc + curr);
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  let left = 0;
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  let rightDiff = {};
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  let leftDiff = {};
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  for (let i = 0; i < nums.length - 1; i++) {
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    left += nums[i];
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    const right = totalSum - left;
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    if (rightDiff[left - right]) rightDiff[left - right]++;
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    else rightDiff[left - right] = 1;
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  }
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  let maxPartition = rightDiff[0] ? rightDiff[0] : 0;
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  left = 0;
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  for (let i = 0; i < nums.length; i++) {
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    left += nums[i];
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    let diff = k - nums[i];
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    const right = totalSum - left;
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    let leftVal = leftDiff[`${diff}`] ? leftDiff[`${diff}`] : 0;
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    let rightVal = rightDiff[`${-diff}`] ? rightDiff[`${-diff}`] : 0;
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    maxPartition = Math.max(maxPartition, leftVal + rightVal);
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    if (leftDiff[left - right]) leftDiff[left - right]++;
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    else leftDiff[left - right] = 1;
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    rightDiff[left - right]--;
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  }
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  return maxPartition;
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};