荷兰国旗划分

src/algorithm/NetherlandsFlag.java

@@ -0,0 +1,57 @@
+package algorithm;
+
+/**
+ * 荷兰国旗问题的划分
+ * arr[L....R] 以arr[R]作为划分值
+ * <arr[R]的在左侧 =arr[R]的在中间 >arr[R]的在右侧
+ *
+ * @author Wen
+ * @date 2022/8/8 22:05
+ */
+public class NetherlandsFlag {
+
+    //返回划分过后=arr[R]的数的左边界和右边界
+    public int[] cal(int[] arr, int L, int R) {
+        if (L > R) {
+            return new int[]{-1, -1};
+        }
+        if (L == R) {
+            return new int[]{L, R};
+        }
+        int index = 0;
+        int less = 0;
+        int large = R;
+        int num = arr[R];
+        while (index <= large) {
+            if (arr[index] == num) {
+                index++;
+                continue;
+            }
+            if (arr[index] < num) {
+                int temp = arr[less];
+                arr[less] = arr[index];
+                arr[index] = temp;
+                less++;
+                index++;
+                continue;
+            }
+            if (arr[index] > num) {
+                int temp = arr[large];
+                arr[large] = arr[index];
+                arr[index] = temp;
+                large--;
+            }
+        }
+        return new int[]{less , large};
+    }
+
+    public static void main(String[] args) {
+        NetherlandsFlag netherlandsFlag = new NetherlandsFlag();
+        int[] source = new int[]{1, 3, 5, 6, 3, 4, 3, 4, 8, 3};
+        netherlandsFlag.cal(source, 0, 9);
+        for (int i : source) {
+            System.out.println(i);
+        }
+    }
+
+}