#768 - Max Chunks To Make Sorted II

Hard • View on LeetCode • View on GitHub

Array Sorting Greedy Stack Monotonic Stack

Problem Description

You are given an integer array arr.

We split arr into some number of chunks (i.e., partitions), and individually sort each chunk.

After concatenating them, the result should equal the sorted array.

Return the largest number of chunks we can make to sort the array.

Solution

/**
 * @param {number[]} arr
 * @return {number}
 */
var maxChunksToSorted = function(arr) {
  const stack = [];

  for (const num of arr) {
    if (stack.length === 0 || stack[stack.length - 1] <= num) {
      stack.push(num);
    } else {
      const max = stack.pop();
      while (stack.length && stack[stack.length - 1] > num) {
        stack.pop();
      }
      stack.push(max);
    }
  }

  return stack.length;
};