From 600c217e9f3a4b446c272faa452639c9557eb12b Mon Sep 17 00:00:00 2001
From: xiaokexiang <xxiaokexiang@gmail.com>
Date: Wed, 12 Jan 2022 14:32:26 +0800
Subject: [PATCH] =?UTF-8?q?=E6=AF=8F=E6=97=A5=E4=B8=80=E9=A2=98?=
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---
 .../common/algorithm/question/Question2.java  | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/question/Question2.java b/spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/question/Question2.java
index 25ed53e..a918602 100644
--- a/spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/question/Question2.java
+++ b/spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/question/Question2.java
@@ -6,4 +6,27 @@
  * 问题描述： 一个数组中只有两种字符'G' & 'B'，想让所有的G或B都放在左侧，但是只能在相邻字符间进行交换，返回最少需要交换多少次
  */
 public class Question2 {
+
+    /**
+     * 当把G放到左边的时候，B自动到右边，那么只需要将第一个G放到index为0的位置，第二个G放到index为1的位置...
+     * 当把B放到左边的时候，G自动到右边，那么只需要将第一个B放到index为0的位置，第二个B放到index为1的位置...
+     * O(N)
+     */
+    private static int run(char[] arr) {
+        int sum1 = 0, i = 0, sum2 = 0, j = 0;
+        for (int a = 0; a < arr.length; a++) {
+            if (arr[a] == 'G') {
+                // 此时和G不匹配，需要计算交换的次数
+                sum1 += a - (i++);
+            } else {
+                sum2 += a - (j++);
+            }
+        }
+        return Math.min(sum1, sum2);
+    }
+
+    public static void main(String[] args) {
+        char[] arr = {'G', 'B', 'B', 'G', 'B', 'G', 'G', 'B', 'B', 'G'};
+        System.out.println(run(arr));
+    }
 }