- Educational Codeforces Round 142 (Rated for Div. 2)
- Educational Codeforces Round 141 (Rated for Div. 2)
- Educational Codeforces Round 140 (Rated for Div. 2)
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- Educational Codeforces Round 138 (Rated for Div. 2)
- Educational Codeforces Round 137 (Rated for Div. 2)
- Educational Codeforces Round 136 (Rated for Div. 2)
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- Educational Codeforces Round 130 (Rated for Div. 2)
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- Educational Codeforces Round 128 (Rated for Div. 2)
- Educational Codeforces Round 127 (Rated for Div. 2)
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- Educational Codeforces Round 125 (Rated for Div. 2)
- Educational Codeforces Round 124 (Rated for Div. 2)
- Educational Codeforces Round 123 (Rated for Div. 2)
- Educational Codeforces Round 122 (Rated for Div. 2)
- Educational Codeforces Round 121 (Rated for Div. 2)
- Educational Codeforces Round 120 (Rated for Div. 2)
- Educational Codeforces Round 119 (Rated for Div. 2)
- Educational Codeforces Round 118 (Rated for Div. 2)
- Educational Codeforces Round 117 (Rated for Div. 2)
- Educational Codeforces Round 116 (Rated for Div. 2)
- Educational Codeforces Round 115 (Rated for Div. 2)
- Educational Codeforces Round 114 (Rated for Div. 2)
- Educational Codeforces Round 113 (Rated for Div. 2)
- Educational Codeforces Round 112 (Rated for Div. 2)
- Harbour.Space Scholarship Contest 2021-2022 (open for everyone, rated, Div. 1 + Div. 2)
- Educational Codeforces Round 111 (Rated for Div. 2)
- Educational Codeforces Round 110 (Rated for Div. 2)
- Educational Codeforces Round 109 (Rated for Div. 2)
- Educational Codeforces Round 108 (Rated for Div. 2)
- Educational Codeforces Round 107 (Rated for Div. 2)
- Educational Codeforces Round 106 (Rated for Div. 2)
- Educational Codeforces Round 105 (Rated for Div. 2)
- Educational Codeforces Round 104 (Rated for Div. 2)
- Educational Codeforces Round 103 (Rated for Div. 2)
- Educational Codeforces Round 102 (Rated for Div. 2)
- Educational Codeforces Round 101 (Rated for Div. 2)
- Educational Codeforces Round 100 (Rated for Div. 2)
- Educational Codeforces Round 99 (Rated for Div. 2)
- Educational Codeforces Round 98 (Rated for Div. 2)
- Educational Codeforces Round 97 (Rated for Div. 2)
- Educational Codeforces Round 96 (Rated for Div. 2)
- Educational Codeforces Round 95 (Rated for Div. 2)
- Educational Codeforces Round 94 (Rated for Div. 2)
- Educational Codeforces Round 93 (Rated for Div. 2)
- Educational Codeforces Round 92 (Rated for Div. 2)
- Educational Codeforces Round 91 (Rated for Div. 2)
- Educational Codeforces Round 90 (Rated for Div. 2)
- Educational Codeforces Round 89 (Rated for Div. 2)
- Educational Codeforces Round 88 (Rated for Div. 2)
- Educational Codeforces Round 87 (Rated for Div. 2)
- Educational Codeforces Round 86 (Rated for Div. 2)
- Educational Codeforces Round 85 (Rated for Div. 2)
- Educational Codeforces Round 84 (Rated for Div. 2)
- Educational Codeforces Round 83 (Rated for Div. 2)
- Educational Codeforces Round 82 (Rated for Div. 2)
- Educational Codeforces Round 81 (Rated for Div. 2)
- Educational Codeforces Round 80 (Rated for Div. 2)
- Educational Codeforces Round 79 (Rated for Div. 2)
- Educational Codeforces Round 78 (Rated for Div. 2)
- Educational Codeforces Round 77 (Rated for Div. 2)
- Educational Codeforces Round 76 (Rated for Div. 2)
- Educational Codeforces Round 75 (Rated for Div. 2)
- Educational Codeforces Round 74 (Rated for Div. 2)
- Educational Codeforces Round 73 (Rated for Div. 2)
- Educational Codeforces Round 72 (Rated for Div. 2)
- Educational Codeforces Round 71 (Rated for Div. 2)
- Educational Codeforces Round 70 (Rated for Div. 2)
- Educational Codeforces Round 69 (Rated for Div. 2)
- Educational Codeforces Round 68 (Rated for Div. 2)
- Educational Codeforces Round 67 (Rated for Div. 2)
- Educational Codeforces Round 66 (Rated for Div. 2)
- Educational Codeforces Round 65 (Rated for Div. 2)
- Educational Codeforces Round 64 (Rated for Div. 2)
- Educational Codeforces Round 63 (Rated for Div. 2)
- Educational Codeforces Round 62 (Rated for Div. 2)
- Educational Codeforces Round 61 (Rated for Div. 2)
- Educational Codeforces Round 60 (Rated for Div. 2)
- Educational Codeforces Round 59 (Rated for Div. 2)
- Educational Codeforces Round 58 (Rated for Div. 2)
- Educational Codeforces Round 57 (Rated for Div. 2)
- Educational Codeforces Round 56 (Rated for Div. 2)
- Educational Codeforces Round 55 (Rated for Div. 2)
- Educational Codeforces Round 54 (Rated for Div. 2)
- Educational Codeforces Round 53 (Rated for Div. 2)
- Educational Codeforces Round 52 (Rated for Div. 2)
- Educational Codeforces Round 51 (Rated for Div. 2)
- Educational Codeforces Round 50 (Rated for Div. 2)
- Educational Codeforces Round 49 (Rated for Div. 2)
- Educational Codeforces Round 48 (Rated for Div. 2)
- Educational Codeforces Round 47 (Rated for Div. 2)
- Educational Codeforces Round 46 (Rated for Div. 2)
- Educational Codeforces Round 45 (Rated for Div. 2)
- Educational Codeforces Round 44 (Rated for Div. 2)
- Educational Codeforces Round 43 (Rated for Div. 2)
- Educational Codeforces Round 42 (Rated for Div. 2)
- Educational Codeforces Round 41 (Rated for Div. 2)
- Educational Codeforces Round 40 (Rated for Div. 2)
- Educational Codeforces Round 39 (Rated for Div. 2)
- Educational Codeforces Round 38 (Rated for Div. 2)
- Educational Codeforces Round 37 (Rated for Div. 2)
- Educational Codeforces Round 36 (Rated for Div. 2)
- Educational Codeforces Round 35 (Rated for Div. 2)
- Educational Codeforces Round 34 (Rated for Div. 2)
- Educational Codeforces Round 33 (Rated for Div. 2)
- Educational Codeforces Round 32
- Educational Codeforces Round 31
- Educational Codeforces Round 30
- Educational Codeforces Round 29
- Educational Codeforces Round 28
- Educational Codeforces Round 27
- Educational Codeforces Round 26
- Educational Codeforces Round 25
- Educational Codeforces Round 24
- Educational Codeforces Round 23
- Educational Codeforces Round 22
- Educational Codeforces Round 21
- Educational Codeforces Round 20
- Educational Codeforces Round 19
- Educational Codeforces Round 18

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If I have understood it correctly, the proof is: Let's solve this problem for a 1D case, then we will extend it to 2D. Say, n = 3. So, the values are: 1, 2, 3, 4, 5, 6, 7, 8, 9 (from 1 to n*n) Here, the minimum value is 1 and the maximum value is 9, so, no matter what, the absolute difference will be at most 8 (when |9-1|) and the minimum absolute difference will be 1 (when |9-8|), and the other values will be in between. Our target is to maximize the total various types of such absolute differences. If we order the numbers in the following way: 9, 1, 8, 2, 7, 3, 6, 4, 5 then the target can be maximized. As in this case we are getting these all kinds of absolute differences we could ever get from them taking side-adjacent values. That are: 8 (i.e, |9-1|), 7 (i.e, |8-1|), 6 (i.e, |8-2|), ..., 1 (i.e, |5-4|) Two numbers in an array are side-adjacent when they are positioned one after another either in the same row or in the same column. For example, for a 5x5 matrix, the indices are as follows:
So, the side adjacent to position (3, 3) are (3, 2), (3, 4), (2, 3), and (4, 3) positions. We have to find all possible side-adjacent positions for each position and take absolute differences of corresponding values and count how many unique absolute difference values we get. And obviously, we have to find an arrangement in such a way, that the number of possible such values maximizes. Going back to 3x3 cases (for better manageability), a deterministic solution is to arrange the 1D array (which maximizes the result in 1D case, i.e: 9, 1, 8, 2, 7, 3, 6, 4, 5), in a zig-zag fashion. So, the solution is:
which follows the following pattern:
This will work because the zig-zag pattern is nothing but the same 1D array (just in an entangled fashion). But the values which were side-adjacent in 1D cases are still side adjacent in 2D cases (if we just follow this path). Obviously, as it is now in 2D, there will be more side-adjacent pairs that are not shown in the path (each position can have at most 4 side-adjacent positions, namely: left, right, up and down position), but we simply don't care for them, as we already have maximized the result and the other side-adjacent values will just create duplicate absolute difference values which we already found while traversing the path. Solution: https://codeforces.com/contest/1783/submission/190766740 |

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In fact we can directly get a formula using lagrange inversion. the final result (plus 2) is the $$$x^{n-1}$$$ coefficient of $$$2(n-1)!(\frac{x}{2x+1-e^x})^n$$$ |

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Oh this $$$O(n)$$$ is better than std's $$$O(n\log n)$$$ :) |

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Through this comment, I want to address the cheating charges levied on me and Numinous , for having a coinciding solution to problem C in Educational Round 142. The submissions are 190386013 and 190353992. The reason for getting plagiarised was having a similar template, going through solve function for both speaks out the difference clearly. I hereby in my humble opinion ask MikeMirzayanov Neon BledDest adedalic vovuh awoo to provide us justice and the ratings we deserve . Thank You for your time and effort . |

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IMO the problems were great. I enjoyed thinking about and solving them. Also I got caught on the special case for B (a1 == 0) haha. |

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Hi my submission 190325251 is said to coincide with submission 190323813. I believe the logic to this problem is very straight forward and the solve() template we both used is very standard. Any of my previous submission uses a similar template + style and I believe this is just a mistake from the automated plagiarism checking system. Please update I dont want to be flagged for cheating :( |

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