fix: counting sort algorithm (#1065)

Author: EthanCai

basic/sorting/CountingSort/CountingSort.go

@@ -1,26 +1,54 @@
 package main
 
+import (
+	"fmt"
+	"log"
+	"time"
+)
+
 func CountingSort(nums []int, min, max int) {
 	n := len(nums)
 	k := max - min + 1
 	c := make([]int, k)
 	for _, v := range nums {
 		c[v-min]++
 	}
+	log.Println(c)
 
 	for i := 1; i < k; i++ {
 		c[i] += c[i-1]
 	}
+	log.Println(c)
 
 	r := make([]int, n)
 	for i := n - 1; i >= 0; i-- {
 		v := nums[i]
-		a := c[v]
-		r[a-1] = v + min
-		c[v]--
+		a := c[v-min]
+		r[a-1] = v
+		c[v-min]--
+		log.Println(r)
 	}
 
 	for i, v := range r {
 		nums[i] = v
 	}
-}
+	log.Println(nums)
+}
+
+func main() {
+	// uncomment following line to enable log print
+	// log.SetOutput(io.Discard)
+
+	// test case 1
+	nums := []int{1, 2, 7, 9, 5, 5, 8}
+	CountingSort(nums, 1, 9)
+	fmt.Println(nums)
+
+	// wait complete output to terminal
+	time.Sleep(time.Second)
+
+	// test case 2
+	nums = []int{3, 7, 9, 5, 5, 8, 11}
+	CountingSort(nums, 3, 11)
+	fmt.Println(nums)
+}

basic/sorting/CountingSort/CountingSort.java

@@ -1,21 +1,38 @@
+import java.util.Arrays;
+
 public class CountingSort {
-    public static void sort(int[] nums, int min, int max) {
+    public static void countingSort(int[] nums, int min, int max) {
         int n = nums.length;
         int k = max - min + 1;
         int[] c = new int[k];
         for (int v : nums) {
             c[v - min]++;
         }
+
         for (int i = 1; i < k; i++) {
             c[i] += c[i - 1];
         }
+
         int[] r = new int[n];
         for (int i = n - 1; i >= 0; i--) {
             int v = nums[i];
-            int a = c[v];
-            r[a - 1] = v + min;
-            c[v]--;
+            int a = c[v - min];
+            r[a - 1] = v;
+            c[v - min]--;
         }
         System.arraycopy(r, 0, nums, 0, n);
     }
-}
+
+    public static void main(String[] args) {
+
+        // test case 1
+        int[] nums = {1, 2, 7, 9, 5, 5, 8};
+        countingSort(nums, 1, 9);
+        System.out.println(Arrays.toString(nums));
+
+        // test case 2
+        int[] nums2 = {2, 7, 9, 5, 5, 8};
+        countingSort(nums2, 2, 9);
+        System.out.println(Arrays.toString(nums2));
+    }
+}

basic/sorting/CountingSort/README.md

@@ -10,67 +10,6 @@
 -   创建结果数组 `r`，起始索引 `i`
 -   遍历数组 `c`，找出其中元素大于 `0` 的元素，将其对应的索引作为元素值填充到 `r` 数组中，每处理一次，`c` 中的元素值减 `1`，直到该元素值不大于 `0`，依次处理 `c` 中剩下的元素
 
-## 代码示例
-
-<!-- tabs:start -->
-
-### **Java**
-
-```java
-public class CountingSort {
-    public static void sort(int[] nums, int min, int max) {
-        int n = nums.length;
-        int k = max - min + 1;
-        int[] c = new int[k];
-        for (int v : nums) {
-            c[v - min]++;
-        }
-        for (int i = 1; i < k; i++) {
-            c[i] += c[i - 1];
-        }
-        int[] r = new int[n];
-        for (int i = n - 1; i >= 0; i--) {
-            int v = nums[i];
-            int a = c[v];
-            r[a - 1] = v + min;
-            c[v]--;
-        }
-        System.arraycopy(r, 0, nums, 0, n);
-    }
-}
-```
-
-### **Go**
-
-```go
-func CountingSort(nums []int, min, max int) {
-	n := len(nums)
-	k := max - min + 1
-	c := make([]int, k)
-	for _, v := range nums {
-		c[v-min]++
-	}
-
-	for i := 1; i < k; i++ {
-		c[i] += c[i-1]
-	}
-
-	r := make([]int, n)
-	for i := n - 1; i >= 0; i-- {
-		v := nums[i]
-		a := c[v]
-		r[a-1] = v + min
-		c[v]--
-	}
-
-	for i, v := range r {
-		nums[i] = v
-	}
-}
-```
-
-<!-- tabs:end -->
-
 ## 算法分析
 
 -   时间复杂度 $O(n+k)$， 其中 $n$ 为排序数组长度，而 $k$ 为排序数组中数值的取值范围，当 $k\lt n$ 时，时间复杂度为 $O(n)$。