🎰 排列组合计算器Permutation & Combination Calculator
计算排列数 nPr、组合数 nCr，以及可重复排列和可重复组合。Compute permutations nPr, combinations nCr, and with-repetition variants.
使用说明与常见问题How-to & FAQ
「排列组合计算器」是什么？What is the Permutation & Combination Calculator tool?
计算排列数 nPr、组合数 nCr，以及可重复排列和可重复组合。Compute permutations nPr, combinations nCr, and with-repetition variants.
如何使用「排列组合计算器」？How do I use the Permutation & Combination Calculator tool?
在「排列组合计算器」中，填写「n (总数)」、「r (选取)」等参数，结果会随输入实时计算并显示在下方。In the Permutation & Combination Calculator: Fill in "n (total)", "r (chosen)"; results are recalculated instantly as you type.
计算精度如何？How precise are the results?
「排列组合计算器」使用 JavaScript 双精度浮点数（约 15–16 位有效数字），部分功能使用 BigInt 处理大整数。The Permutation & Combination Calculator uses double-precision floating point (about 15–16 significant digits); some features use BigInt for large integers.
「排列组合计算器」免费吗？需要注册吗？Is the Permutation & Combination Calculator free? Do I need an account?
「排列组合计算器」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Permutation & Combination Calculator is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.