Merge pull request #407 from milesmao233/master

add javascript bucketSort and countingSort

Author: wangzheng0822

javascript/13_sorts/bucketSort.js

@@ -0,0 +1,70 @@
+// 思路：
+// 将数组中的数据，按桶进行划分，将相邻的数据划分在同一个桶中
+// 每个桶用插入排序算法（或者快速排序）进行排序
+// 最后整合每个桶中的数据
+
+function bucketSort(array, bucketSize = 5) {
+    if (array.length < 2) {
+        return array
+    }
+    const buckets = createBuckets(array, bucketSize)
+    return sortBuckets(buckets)
+}
+
+function createBuckets(array, bucketSize) {
+    let minValue = array[0]
+    let maxValue = array[0]
+    // 遍历数组，找到数组最小值与数组最大值
+    for (let i = 1; i < array.length; i++) {
+        if (array[i] < minValue) {
+            minValue = array[i]
+        } else if (array[i] > maxValue) {
+            maxValue = array[i]
+        }
+    }
+    // 根据最小值、最大值、桶的大小，计算得到桶的个数
+    const bucketCount = Math.floor((maxValue - minValue) / bucketSize) + 1
+    // 建立一个二维数组，将桶放入buckets中
+    const buckets = []
+    for (let i = 0; i < bucketCount; i++) {
+        buckets[i] = []
+    }
+    // 计算每一个值应该放在哪一个桶中
+    for (let i = 0; i < array.length; i++) {
+        const bucketIndex = Math.floor((array[i] - minValue) / bucketSize)
+        buckets[bucketIndex].push(array[i])
+    }
+    return buckets
+}
+
+function sortBuckets(buckets) {
+    const sortedArray = []
+    for (let i = 0; i < buckets.length; i++) {
+        if (buckets[i] != null) {
+            insertionSort(buckets[i])
+            sortedArray.push(...buckets[i])
+        }
+    }
+    return sortedArray
+}
+
+// 插入排序
+function insertionSort(array) {
+    const { length } = array
+    if (length <= 1) return
+
+    for (let i = 1; i < length; i++) {
+        let value = array[i]
+        let j = i - 1
+
+        while (j >= 0) {
+            if (array[j] > value) {
+                array[j + 1] = array[j] // 移动
+                j--
+            } else {
+                break
+            }
+        }
+        array[j + 1] = value // 插入数据
+    }
+}

javascript/13_sorts/countingSort.js

@@ -0,0 +1,38 @@
+const countingSort = array => {
+    if (array.length <= 1) return
+
+    const max = findMaxValue(array)
+    const counts = new Array(max + 1)
+
+    // 计算每个元素的个数，放入到counts桶中
+    // counts下标是元素，值是元素个数
+    array.forEach(element => {
+        if (!counts[element]) {
+            counts[element] = 0
+        }
+        counts[element]++
+    })
+
+    // counts下标是元素，值是元素个数
+    // 例如： array: [6, 4, 3, 1], counts: [empty, 1, empty, 1, 1, empty, 1]
+    // i是元素, count是元素个数
+    let sortedIndex = 0
+    counts.forEach((count, i) => {
+        while (count > 0) {
+            array[sortedIndex] = i
+            sortedIndex++
+            count--
+        }
+    })
+    // return array
+}
+
+function findMaxValue(array) {
+    let max = array[0]
+    for (let i = 1; i < array.length; i++) {
+        if (array[i] > max) {
+            max = array[i]
+        }
+    }
+    return max
+}