POJ 2299 Ultra-QuickSort

Posted 2022-06-29 zaq19970105

题目链接：https://vjudge.net/problem/POJ-2299

题目大意

　　归并排序求逆序数经典题。

分析

　　略。

代码如下

  1 #include <cmath>
  2 #include <ctime>
  3 #include <iostream>
  4 #include <string>
  5 #include <vector>
  6 #include <cstdio>
  7 #include <cstdlib>
  8 #include <cstring>
  9 #include <queue>
 10 #include <map>
 11 #include <set>
 12 #include <algorithm>
 13 #include <cctype>
 14 #include <stack>
 15 #include <deque>
 16 #include <list>
 17 #include <sstream>
 18 #include <cassert>
 19 using namespace std;
 20  
 21 #define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
 22 #define Rep(i,n) for (int i = 0; i < (int)(n); ++i)
 23 #define For(i,s,t) for (int i = (int)(s); i <= (int)(t); ++i)
 24 #define rFor(i,t,s) for (int i = (int)(t); i >= (int)(s); --i)
 25 #define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i)
 26 #define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i)
 27 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
 28 #define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i)
 29  
 30 #define pr(x) cout << #x << " = " << x << "  "
 31 #define prln(x) cout << #x << " = " << x << endl
 32  
 33 #define LOWBIT(x) ((x)&(-x))
 34  
 35 #define ALL(x) x.begin(),x.end()
 36 #define INS(x) inserter(x,x.begin())
 37 #define UNIQUE(x) x.erase(unique(x.begin(), x.end()), x.end())
 38 #define REMOVE(x, c) x.erase(remove(x.begin(), x.end(), c), x.end()); // 删去 x 中所有 c 
 39 #define TOLOWER(x) transform(x.begin(), x.end(), x.begin(),::tolower);
 40 #define TOUPPER(x) transform(x.begin(), x.end(), x.begin(),::toupper);
 41  
 42 #define ms0(a) memset(a,0,sizeof(a))
 43 #define msI(a) memset(a,0x3f,sizeof(a))
 44 #define msM(a) memset(a,-1,sizeof(a))
 45 
 46 #define MP make_pair
 47 #define PB push_back
 48 #define ft first
 49 #define sd second
 50  
 51 template<typename T1, typename T2>
 52 istream &operator>>(istream &in, pair<T1, T2> &p) 
 53     in >> p.first >> p.second;
 54     return in;
 55 
 56  
 57 template<typename T>
 58 istream &operator>>(istream &in, vector<T> &v) 
 59     for (auto &x: v)
 60         in >> x;
 61     return in;
 62 
 63 
 64 template<typename T>
 65 ostream &operator<<(ostream &out, vector<T> &v) 
 66     Rep(i, v.size()) out << v[i] << " \n"[i == v.size()];
 67     return out;
 68 
 69  
 70 template<typename T1, typename T2>
 71 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) 
 72     out << "[" << p.first << ", " << p.second << "]" << "\n";
 73     return out;
 74 
 75 
 76 inline int gc()
 77     static const int BUF = 1e7;
 78     static char buf[BUF], *bg = buf + BUF, *ed = bg;
 79     
 80     if(bg == ed) fread(bg = buf, 1, BUF, stdin);
 81     return *bg++;
 82  
 83 
 84 inline int ri()
 85     int x = 0, f = 1, c = gc();
 86     for(; c<48||c>57; f = c==‘-‘?-1:f, c=gc());
 87     for(; c>47&&c<58; x = x*10 + c - 48, c=gc());
 88     return x*f;
 89 
 90 
 91 template<class T>
 92 inline string toString(T x) 
 93     ostringstream sout;
 94     sout << x;
 95     return sout.str();
 96 
 97 
 98 inline int toInt(string s) 
 99     int v;
100     istringstream sin(s);
101     sin >> v;
102     return v;
103 
104 
105 //min <= aim <= max
106 template<typename T>
107 inline bool BETWEEN(const T aim, const T min, const T max) 
108     return min <= aim && aim <= max;
109 
110  
111 typedef long long LL;
112 typedef unsigned long long uLL;
113 typedef vector< int > VI;
114 typedef vector< bool > VB;
115 typedef vector< char > VC;
116 typedef vector< double > VD;
117 typedef vector< string > VS;
118 typedef vector< LL > VL;
119 typedef vector< VI > VVI;
120 typedef vector< VB > VVB;
121 typedef vector< VS > VVS;
122 typedef vector< VL > VVL;
123 typedef vector< VVI > VVVI;
124 typedef vector< VVL > VVVL;
125 typedef pair< int, int > PII;
126 typedef pair< LL, LL > PLL;
127 typedef pair< int, string > PIS;
128 typedef pair< string, int > PSI;
129 typedef pair< string, string > PSS;
130 typedef pair< double, double > PDD;
131 typedef vector< PII > VPII;
132 typedef vector< PLL > VPLL;
133 typedef vector< VPII > VVPII;
134 typedef vector< VPLL > VVPLL;
135 typedef vector< VS > VVS;
136 typedef map< int, int > MII;
137 //typedef unordered_map< int, int > uMII;
138 typedef map< LL, LL > MLL;
139 typedef map< string, int > MSI;
140 typedef map< int, string > MIS;
141 typedef set< int > SI;
142 typedef stack< int > SKI;
143 typedef queue< int > QI;
144 typedef priority_queue< int > PQIMax;
145 typedef priority_queue< int, VI, greater< int > > PQIMin;
146 const double EPS = 1e-8;
147 const LL inf = 0x7fffffff;
148 const LL infLL = 0x7fffffffffffffffLL;
149 const LL mod = 1e9 + 7;
150 const int maxN = 5e5 + 7;
151 const LL ONE = 1;
152 const LL evenBits = 0xaaaaaaaaaaaaaaaa;
153 const LL oddBits = 0x5555555555555555;
154 
155 int a[maxN], b[maxN], N;
156 LL ans;
157 
158 void Merge(int l, int mid, int r) 
159     int i = l, j = mid + 1, k = l;
160     while(i <= mid && j <= r) 
161         if(a[i] <= a[j]) b[k++] = a[i++];
162         else 
163             b[k++] = a[j++];
164             ans += (LL)(mid - i + 1);
165            
166     
167     while(i <= mid) b[k++] = a[i++];
168     while(j <= r) b[k++] = a[j++];
169     For(h, l, r) a[h] = b[h];
170 
171 
172 void MergeSort(int l, int r) 
173     if(l >= r) return;
174     int mid = (l + r) >> 1;
175     
176     MergeSort(l, mid);
177     MergeSort(mid + 1, r);
178     Merge(l, mid, r);
179 
180 
181 int main()
182     //freopen("MyOutput.txt","w",stdout);
183     //freopen("input.txt","r",stdin);
184     //INIT();
185     while(scanf("%d", &N) && N)    
186         ans = 0;
187         Rep(i, N) scanf("%d", &a[i]);
188         MergeSort(0, N - 1);
189         printf("%lld\n", ans);
190     
191     return 0;
192 

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