Challenges-Unlock

#1

I am not able to unserstand how to apply greedy approach in this question.

#2

the following problem can be easily solved by using hashmap or unordered map. The hint to solve the problem is that the given array will always contain permutation of the first N natural numbers. So we will prepare a map which will contain element as the key and the index at which it is present as the value.
Algorithm

Create the map by filling the number as the key and the index at which it is present as the value
Iterate over the whole array.
For element at a particular index m we will check if it is present at its best spot or not.
The best spot of any number num is the N-num index of the array.
If the number is not present at its best spot then we will swap the number with element present at that spot.
As we have stored the index of every element in the map we can easily retrieve that from the map to get the swap done.

You can take a look at this code for reference https://ide.codingblocks.com/s/279453

#3

But How we can get to know about N num indexing . Like a number 50 for example in array with a size of less than 50 should be placed where?

#4

We won’t have a number 50 in that case.
We are given a permutation of first n integers only. Read the question again.

#5

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