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GCD and LCMMediumWrite codeWrite codeMedium18 minPrime exponent in factorialMediumWrite codeWrite codeMedium22 minSum of divisorsMediumWrite codeWrite codeMedium20 minSmallest prime factorMediumWrite codeWrite codeMedium15 minMaximum pair GCDMediumWrite codeWrite codeMedium25 minFactorial digit countMediumWrite codeWrite codeMedium20 minDivisor count functionMediumWrite codeWrite codeMedium20 minSingle-bit error correctionMediumWrite codeWrite codeMedium22 minUnpack signed converter samplesMediumWrite codeWrite codeMedium22 minBitmap block allocatorHardWrite codeApple styleWrite codeApple styleHard35 minIndex intersection mergeHardWrite codeOracle styleWrite codeOracle styleHard30 minBinomial coefficient modulo primeHardWrite codeCitadel styleWrite codeCitadel styleHard35 minModular multiplicative inverseHardWrite codeWrite codeHard30 minMaximum XOR subsetHardWrite codeWrite codeHard35 minGeneralized Chinese remainder theoremHardWrite codeWrite codeHard35 minLongest subarray GCDHardWrite codeWrite codeHard35 minChinese remainder theoremHardWrite codeCitadel styleWrite codeCitadel styleHard35 minPrimes in rangeHardWrite codeCitadel styleWrite codeCitadel styleHard30 minExtended Euclidean algorithmHardWrite codeWrite codeHard30 minCatalan number modulo primeHardWrite codeCitadel styleWrite codeCitadel styleHard30 minMiller-Rabin primality testHardWrite codeCitadel styleWrite codeCitadel styleHard35 minGeometric series moduloHardWrite codeWrite codeHard30 minFibonacci moduloHardWrite codeWrite codeHard35 minCoprime pairs mobius inversionHardWrite codeWrite codeHard35 minDiscrete logarithm modulo primeHardWrite codeWrite codeHard40 minSolve two congruencesHardWrite codeWrite codeHard35 min
Every employee with their departmentEasySQLSQLEasy8 minHeadcount per departmentEasySQLSQLEasy8 minOrders per statusEasySQLSQLEasy7 minThe highest and lowest salary on recordEasySQLSQLEasy7 minWho has no salary recordedEasySQLSQLEasy8 minOrders with the customer countryEasySQLSQLEasy8 minHow many of each eventEasySQLSQLEasy7 minMonthly revenue from live subscriptionsEasySQLSQLEasy8 minPosts with their authorEasySQLSQLEasy8 minAuthors with no country on fileEasySQLSQLEasy8 minHow many students per courseEasySQLSQLEasy8 minDepartments with nobody in themMediumSQLSQLMedium10 minThe average that a NULL salary ruinsMediumSQLSQLMedium10 minCustomers who spent over a thresholdMediumSQLSQLMedium10 minEveryone and their managerMediumSQLSQLMedium12 minSalaries paid to more than one personMediumSQLSQLMedium10 minPaid more than their department averageMediumSQLSQLMedium12 minRevenue by monthMediumSQLSQLMedium10 minA salary column with no blanksMediumSQLSQLMedium9 minHires per yearMediumSQLSQLMedium10 minManagers onlyMediumSQLSQLMedium10 minPayroll by department, biggest firstMediumSQLSQLMedium10 minCustomers who never orderedMediumSQLSQLMedium10 minAverage order value by countryMediumSQLSQLMedium10 min