Next Permutation of Array in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Next Permutation algorithm?

It finds the next lexicographically greater permutation of an array of numbers. If no such permutation exists, it rearranges the array to the lowest possible order (sorted ascending).

intermediate

In the Next Permutation algorithm, what is the significance of finding the 'pivot' index?

The pivot is the first index from the right where the number is smaller than the number immediately after it. It marks where the next permutation change starts.

intermediate

Why do we reverse the suffix of the array after swapping the pivot with the right element?

Because the suffix is in descending order, reversing it makes it the smallest ascending order, ensuring the next permutation is just one step bigger.

beginner

What happens if the entire array is in descending order when applying Next Permutation?

It means the array is the highest permutation. The algorithm reverses the entire array to the lowest permutation (ascending order).

beginner

Show the step-by-step next permutation for the array [1, 3, 2].

1. Find pivot: index 0 (1 < 3). 2. Find element to swap with pivot: index 2 (2 > 1). 3. Swap: [2, 3, 1]. 4. Reverse suffix after pivot: reverse [3, 1] to [1, 3]. 5. Result: [2, 1, 3].

What is the first step in finding the next permutation of an array?

A Find the first index from the right where the number is smaller than the next number

B Reverse the entire array

C Sort the array in ascending order

D Swap the first and last elements

The first step is to find the pivot index where the number is smaller than the next number from the right.

If no pivot is found in the array, what does the Next Permutation algorithm do?

A Reverses the entire array to ascending order

B Swaps the first two elements

C Sorts the array in descending order

D Returns the array as is

If no pivot is found, the array is in descending order, so the algorithm reverses it to ascending order.

After swapping the pivot, what is the next step in the Next Permutation algorithm?

A Sort the entire array

B Reverse the suffix after the pivot

C Swap the first and last elements

D Do nothing

The suffix after the pivot is reversed to get the smallest ascending order.

What does the Next Permutation algorithm guarantee about the output array?

A It is sorted in descending order

B It is the smallest permutation possible

C It is the next lexicographically greater permutation

D It is the same as the input array

The algorithm finds the next lexicographically greater permutation or the smallest if none exists.

Given the array [1, 2, 3], what is the next permutation?

A [2, 1, 3]

B [3, 2, 1]

C [1, 2, 3]

D [1, 3, 2]

The next permutation after [1, 2, 3] is [1, 3, 2].

Explain the steps of the Next Permutation algorithm in your own words.

Think about how to get the next bigger arrangement of numbers.

Why do we reverse the suffix after swapping in the Next Permutation algorithm?

Consider the order of numbers after the pivot.