Max Chunks To Make Sorted in C++

Suppose we gave an array arr that is a permutation of [0, 1, ..., arr.length - 1], we have to split the array into some number of "chunks" or partitions, and individually sort each partition. So after concatenating them, the result will be the sorted array. So if the array is like [1,0,2,3,4], then the output will be 4, as we can split into two partitions like [1, 0] and [2,3,4], but this can also be true that [1, 0], [2], [3], [4]. So this is the highest number of chunks possible, so output is 4.

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

To solve this, we will follow these steps −

• ans := 0, minVal := inf, n := size of arr, and maxVal := -inf
• for i in range 0 to n
  • maxVal := max of arr[i] and maxVal
  • if maxVal = i, then increase ans by 1
• return ans

Example

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
   int maxChunksToSorted(vector<int>& arr) {
      int ans = 0;
      int minVal = INT_MAX;
      int n = arr.size();
      int maxVal = INT_MIN;
      for(int i = 0; i < n; i++){
         maxVal = max(arr[i], maxVal);
         if(maxVal == i){
            ans++;
         }
      }
      return ans;
   }
};
main(){
   Solution ob;
   vector<int> v = {1,0,2,3,4};
   cout << (ob.maxChunksToSorted(v));
}

Input

[1,0,2,3,4]

Output

4