具有中间结果的阶乘 - Swift 游乐场 - 索引超出范围错误

Question

看久了都瞎了。无法发现错误。调用函数 factorialIntermediateResults(n: 4) 时出现 "index out of range" 错误希望有人能用新的眼光看一下并帮助我发现错误。谢谢！

func factorialIntermediateResults(n: Int) -> [Int] {
    if n == 0 || n == 1 { return [1] }
    var results = [Int]()
    doAllFactorials(n, &results, 0)
    return results
}

func doAllFactorials(_ n: Int, _ results: inout [Int], _ level: Int) -> Int {
    if n > 1 {
        results[level] = n * doAllFactorials(n-1, &results, level+1)
        return results[level]
    } else {
        results[level] = 1
        return 1
    }
}

factorialIntermediateResults(n: 4)

Answer 1

results 是一个空数组，但您尝试访问值而不先附加值。

最简单的解决方案可能是用零预填充数组。

var results: [Int] = Array(repeating: 0, count: n)

具有中间结果的阶乘 - Swift 游乐场 - 索引超出范围错误

Factorial with intermediate results - Swift playgrounds - index out of range error

factorial

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