From 6acad9f13ba8f51c6563f274244c8b34c46eadfd Mon Sep 17 00:00:00 2001
From: Zengtudor <Zengtudor@outlook.com>
Date: Mon, 1 Sep 2025 12:16:57 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20=E6=B7=BB=E5=8A=A0P3608.cpp=E5=AE=9E?=
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实现基于树状数组的逆序对统计功能，用于检测序列中的不平衡元素。
通过排序和离散化处理输入数据，计算每个元素左右两侧的逆序对数量，
并判断是否满足不平衡条件（max(l,r) > min(l,r)*2）。
---
 EOF             |  0
 src/9/P3608.cpp | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 EOF
 create mode 100644 src/9/P3608.cpp

diff --git a/EOF b/EOF
new file mode 100644
index 0000000..e69de29
diff --git a/src/9/P3608.cpp b/src/9/P3608.cpp
new file mode 100644
index 0000000..76520b3
--- /dev/null
+++ b/src/9/P3608.cpp
@@ -0,0 +1,65 @@
+#include <algorithm>
+#include <cstdint>
+#include <cstdio>
+#include <iostream>
+#include <istream>
+#include <map>
+#include <vector>
+using ll = int64_t;
+
+ll n,ans=0;
+std::vector<ll> a,raw;
+std::map<ll, ll> m;
+std::vector<ll> t;
+
+static inline constexpr ll lb(ll n){
+    return n&(-n);
+}
+
+static inline void upd(ll idx, ll add){
+    while(idx<=n){
+        t[idx]+=add;
+        idx+=lb(idx);
+    }
+}
+
+static inline ll get(ll idx){
+    ll res=0;
+    while(idx){
+        res+=t[idx];
+        idx-=lb(idx);
+    }
+    return res;
+}
+
+int main(){
+    std::iostream::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::cin>>n;
+    raw.resize(n+1);
+    t.resize(n+1);
+    for(ll i=1;i<=n;++i){
+        std::cin>>raw[i];
+    }
+    a=raw;
+    std::sort(a.begin()+1,a.end());
+    for(ll i=1;i<=n;i++){
+        m[a[i]]=i;
+    }
+    for(ll i=1;i<=n;i++){
+        raw[i]=m[raw[i]];
+        // printf("raw[%lld]=%lld\n",i,raw[i]);
+    }
+    for(ll i=1;i<=n;i++){
+        ll g=n-raw[i];
+        ll l=i-1-get(raw[i]);
+        ll r = g-l;
+        // printf("i=%lld, l=%lld, r=%lld\n",i,l,r);
+        if(std::max(l,r)>std::min(l,r)*2){
+            ans++;
+        }
+        upd(raw[i],1);
+    }
+    std::cout<<ans<<"\n";
+}
\ No newline at end of file