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Step 1 : Introduction to the question “What word is a dish with food put between two slices of bread?“ …The word “sandwich” was first used in the late 1700s and refers to John Montagu, the Fourth Earl of Sandwich. Montagu was a noble in charge of the town of Sandwich, Kent, England, and is believed … Read more

Palindromic Indices solution codeforces You are given a palindromic string ss of length nn. You have to count the number of indices ii (1≤i≤n)(1≤i≤n) such that the string after removing sisi from ss still remains a palindrome. For example, consider ss = “aba” If we rem ove s1s1 from ss, the string becomes “ba” which is not a palindrome. If we remove s2s2 from ss, the string becomes “aa” which is a palindrome. If … Read more

AND Sorting solution codeforces You are given a permutation pp of integers from 00 to n−1n−1 (each of them occurs exactly once). Initially, the permutation is not sorted (that is, pi>pi+1pi>pi+1 for at least one 1≤i≤n−11≤i≤n−1). The permutation is called XX-sortable for some non-negative integer XX if it is possible to sort the permutation by performing the operation below some finite number of times: Choose two indices ii and jj (1≤i<j≤n)(1≤i<j≤n) such that pi&pj=Xpi&pj=X. Swap pipi and pjpj. … Read more

LIS or Reverse LIS? solution codeforces You are given an array aa of nn positive integers. Let LIS(a)LIS(a) denote the length of longest strictly increasing subsequence of aa. For example, LIS([2,1–,1,3–])LIS([2,1_,1,3_]) = 22. LIS([3–,5–,10–––,20–––])LIS([3_,5_,10_,20_]) = 44. LIS([3,1–,2–,4–])LIS([3,1_,2_,4_]) = 33. We define array a′a′ as the array obtained after reversing the array aa i.e. a′=[an,an−1,…,a1]a′=[an,an−1,…,a1]. The beauty of array aa is defined as min(LIS(a),LIS(a′))min(LIS(a),LIS(a′)). Your task is to determine the maximum possible beauty of the array aa if you can rearrange … Read more

Unordered Swaps solution codeforces Alice had a permutation pp of numbers from 11 to nn. Alice can swap a pair (x,y)(x,y) which means swapping elements at positions xx and yy in pp (i.e. swap pxpx and pypy). Alice recently learned her first sorting algorithm, so she decided to sort her permutation in the minimum number of swaps possible. She wrote down all the swaps in the order in which she performed them to … Read more

Which pop star did NOT marry and later divorce one of their backup dancers? What do you get when you put beautiful celebrities in close proximity with their stunning backup dancers? You get a whole lot of romance and drama. If Dirty Dancing and Step Up taught us anything, it’s that even the unlikeliest of … Read more