title

problem link

Given an array arr that is a permutation of [0, 1, …, arr.length - 1], we split the array into some number of “chunks” (partitions), and individually sort each chunk. After concatenating them, the result equals the sorted array.

What is the most number of chunks we could have made?

Example 1:

Input: arr = [4,3,2,1,0]
Output: 1

Explanation: Splitting into two or more chunks will not return the required result. For example, splitting into [4, 3], [2, 1, 0] will result in [3, 4, 0, 1, 2], which isn’t sorted.

Example 2:

Input: arr = [1,0,2,3,4]
Output: 4

Explanation: We can split into two chunks, such as [1, 0], [2, 3, 4]. However, splitting into [1, 0], [2], [3], [4] is the highest number of chunks possible.

solution

求多少个chunk， 每个individually sort each chunk. After concatenating them, the result equals the sorted array.

比较当前最大值即可

class Solution {
    public int maxChunksToSorted(int[] arr) {
        int ans = 0, max = 0;
        for (int i = 0; i < arr.length; ++i) {
            max = Math.max(max, arr[i]);
            if (max == i) ans++;
        }
        return ans;
    }
}