第 30 题：请把俩个数组 [A1, A2, B1, B2, C1, C2, D1, D2] 和 [A, B, C, D]，合并为 [A1, A2, A, B1, B2, B, C1, C2, C, D1, D2, D]。

function concatArr (arr1, arr2) { const arr = [...arr1]; let currIndex = 0; for (let i = 0; i < arr2.length; i++) { const RE = new RegExp(arr2[i]) while(currIndex < arr.length) { ++currIndex if (!RE.test(arr[currIndex])) { arr.splice(cur...

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