彩票中奖率的真相：用 JavaScript 看透彩票背后的随机算法（下）

function letterToCode(letterStr) {
  const result = []
  const letters = 'abcdefghijklmnopqrstuvwxyzABCDEFG'
  for (let i = 0; i < letterStr.length; i++) {
    result.push((letters.indexOf(letterStr[i]) + 1).toString().padStart(2, '0'))
  }
  return result
}
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// 服务器集群数量
const machineCount = 100
// 总访问量，50%中的号码才会上报
const totalVisit = 50000000 * 0.5 // 25000000
// 总的时间，因为我们计算的是 10个小时的时间，所以应该计算的总秒数为 36000 秒！
const totalSeconds = 10 * 60 * 60
console.log(totalVisit / totalSeconds / machineCount) // 6.944444444444445
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function random(count) {
  let result = []
  for (let i = 0; i < count; i++) {
    const index = Math.floor(Math.random() * firstDataList.length)
    console.log(firstDataList[index])
    result.push(letterToCode(firstDataList[index]))
  }
  return result
}
console.log(random(2))
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/**
 * @param {String[]} target ['01', '02', '03', '04', '05', '06', '07']
 * @param {String[]} origin ['01', '02', '03', '04', '05', '06', '07']
 * @returns {Number} 返回当前彩票的中奖金额
 */
function compareToMoney(target, origin) {
  let money = 0
  let rightMatched = target[6] === origin[6]
  // 求左边六位的交集数量
  let leftMatchCount = target.slice(0, 6).filter(
    c => origin.slice(0,6).includes(c)
  ).length
  if (leftMatchCount === 6 && rightMatched) {
    money += 5000000
  } else if (leftMatchCount === 6 && !rightMatched) {
    money += 300000
  } else if (leftMatchCount === 5 && rightMatched) {
    money += 3000
  } else if (leftMatchCount === 5 && !rightMatched) {
    money += 200
  } else if (leftMatchCount === 4 && rightMatched) {
    money += 200
  } else if (leftMatchCount === 4 && !rightMatched) {
    money += 10
  } else if (leftMatchCount === 3 && rightMatched) {
    money += 10
  } else if (leftMatchCount === 2 && rightMatched) {
    money += 5
  } else if (leftMatchCount === 1 && rightMatched) {
    money += 5
  } else if (rightMatched) {
    money += 5
  }
  return money
}
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function getRandomCode(count = 500000) {
  const arrRed = Array.from({ length: 33 }, (_, index) => (index + 1).toString().padStart(2, '0'))
  // generateCombinations 是我们上面定义过的函数
  const arrRedResult = generateCombinations(arrRed, 6, count)
  const result = []
  let blue = 1
  arrRedResult.forEach(line => {
    result.push([...line, (blue++).toString().padStart(2, '0')])
    if (blue > 16) {
      blue = 1
    }
  })
  return result
}
function randomPurchase() {
  const codes = getRandomCode()
  const result = []
  for (let code of codes) {
    let count = Math.floor(Math.random() * 50)
    result.push({
      code,
      count,
    })
  }
  return result
}
console.log(randomPurchase())
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[
  {
    code: [
      '01', '02',
      '03', '04',
      '05', '10',
      '05'
    ],
    count: 17
  },
  {
    code: [
      '01', '02',
      '03', '04',
      '05', '11',
      '06'
    ],
    count: 4
  }
]
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// 空号在前，购买数量越多越靠后
const purchaseList = randomPurchase().sort((a, b) => a.count - b.count)
const bonusPool = []
for (let i = 0; i < purchaseList.length; i++) {
  // 假设这就是一等奖，那么就需要计算其价值
  const firstPrize = purchaseList[0]
  let totalMoney = 0
  for (let j = 0; j < purchaseList.length; j++) {
    // 与一等奖进行对比，对比规则是参照彩票中奖规则
    const money = compareToMoney(purchaseList[j].code, firstPrize.code) * purchaseList[j].count
    totalMoney += money
  }
  bonusPool.push({
    code: firstPrize.code,
    totalMoney,
  })
}
const result = bonusPool.sort((a, b) => a.totalMoney - b.totalMoney)
// 至于怎么挑，那就随心所欲了
console.log(result[0].code, result[0].totalMoney)
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