feat: 添加归并排序

sort/merge-sort.mjs

@@ -0,0 +1,42 @@
+/**
+ * @description 不修改原数组，返回新数组
+ * @param {number[]} left - 需要合并的左数组
+ * @param {number[]} right - 需要合并的右数组
+ */
+ export function mergeSort(arr) {
+    if (arr.length <= 1) {
+        return arr; // 已经有序
+    }
+
+    // 分解
+    const middle = Math.floor(arr.length / 2);
+    const left = arr.slice(0, middle);
+    const right = arr.slice(middle);
+
+    // 递归地对左右两部分进行归并排序
+    const sortedLeft = mergeSort(left);
+    const sortedRight = mergeSort(right);
+
+    // 合并
+    return merge(sortedLeft, sortedRight);
+}
+
+function merge(left, right) {
+    let result = [];
+    let leftIndex = 0;
+    let rightIndex = 0;
+
+    // 比较两个数组的元素，将较小的元素加入结果数组
+    while (leftIndex < left.length && rightIndex < right.length) {
+        if (left[leftIndex] < right[rightIndex]) {
+            result.push(left[leftIndex]);
+            leftIndex++;
+        } else {
+            result.push(right[rightIndex]);
+            rightIndex++;
+        }
+    }
+
+    // 将剩余的元素加入结果数组
+    return result.concat(left.slice(leftIndex), right.slice(rightIndex));
+}