标签：long app append 影响 不能 number 含义 nbsp log
[UOJ#223][BZOJ4654][Noi2016]国王饮水记
试题描述
输入
输出
输入示例
3 1 3 1 4 3
输出示例
2.666667
数据规模及约定
见“输入”
题解
这题居然被我卡过了 233333333
这题 91 分还是比较有意义的。
首先发现一个性质（以下所说的数组 H 均不包含城市 1 的高度以及比城市 1 矮的高度），若将数组 H 从小到大排序，会发现最优策略一定考虑最后面若干个数，并且 k 次取平均操作均是和一段连续区间取平均。
那么一个 dp 的模型就已经出来了：f(j, i) 表示进行了 j 次取平均操作，前 i 个数都被考虑过的最大能达到的平均值。
转移就是枚举这一次取平均操作是哪个区间：f(j, i) = max{ ( S[i] - S[k] + f(j-1, k) ) / ( i - k + 1 ) | 0 ≤ k < i }，整理一下发现 f(j, i) = ( S[i] - ( S[k] - f(j-1, k) ) ) / ( i - ( k - 1 ) )，也就是说我们要最大化一个斜率，那么显然就是对于点集 { ( x - 1, S[x] - f(x-1, k) ) } 维护下凸壳。
进一步发现，每次转移的决策是单调增的，因为我们已经将数组 H 从小到大排序，那么点集 { ( i, S[i] ) } 构成了一个下凸壳，所以每次过 ( i, S[i] ) 的直线只会更陡，并且（画个图就知道）在维护的凸包上的切点一直在往后移。
于是初步分析我们得到 O(nkp) 的算法。
看到题解，我了解到当 k > 14 时，只需要算到 j = 14 即可，后面的转移都是长度为 1 的区间，贪心取即可。这样试了一下有 90 分。。。
后来我尝试卡常，发现我被骗了，其实只需要算到 j = 8（也许更少，现在(2017-6-30) AC 的代码只算到了 j = 8，欢迎 hack），然后题面中时刻需要保留 6/5·p 位小数也是骗人的，我只保留了 3050 位小数就过掉最后一个点了。。。
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <algorithm>
#include <string>
// ---------- decimal lib start ----------
const int PREC = 3050;
class Decimal {
public:
Decimal();
Decimal(const std::string &s);
Decimal(const char *s);
Decimal(int x);
Decimal(long long x);
Decimal(double x);
bool is_zero() const;
// p (p > 0) is the number of digits after the decimal point
std::string to_string(int p) const;
double to_double() const;
friend Decimal operator + (const Decimal &a, const Decimal &b);
friend Decimal operator + (const Decimal &a, int x);
friend Decimal operator + (int x, const Decimal &a);
friend Decimal operator + (const Decimal &a, long long x);
friend Decimal operator + (long long x, const Decimal &a);
friend Decimal operator + (const Decimal &a, double x);
friend Decimal operator + (double x, const Decimal &a);
friend Decimal operator - (const Decimal &a, const Decimal &b);
friend Decimal operator - (const Decimal &a, int x);
friend Decimal operator - (int x, const Decimal &a);
friend Decimal operator - (const Decimal &a, long long x);
friend Decimal operator - (long long x, const Decimal &a);
friend Decimal operator - (const Decimal &a, double x);
friend Decimal operator - (double x, const Decimal &a);
friend Decimal operator * (const Decimal &a, int x);
friend Decimal operator * (int x, const Decimal &a);
friend Decimal operator / (const Decimal &a, int x);
friend bool operator < (const Decimal &a, const Decimal &b);
friend bool operator > (const Decimal &a, const Decimal &b);
friend bool operator <= (const Decimal &a, const Decimal &b);
friend bool operator >= (const Decimal &a, const Decimal &b);
friend bool operator == (const Decimal &a, const Decimal &b);
friend bool operator != (const Decimal &a, const Decimal &b);
Decimal & operator += (int x);
Decimal & operator += (long long x);
Decimal & operator += (double x);
Decimal & operator += (const Decimal &b);
Decimal & operator -= (int x);
Decimal & operator -= (long long x);
Decimal & operator -= (double x);
Decimal & operator -= (const Decimal &b);
Decimal & operator *= (int x);
Decimal & operator /= (int x);
friend Decimal operator - (const Decimal &a);
// These can‘t be called
friend Decimal operator * (const Decimal &a, double x);
friend Decimal operator * (double x, const Decimal &a);
friend Decimal operator / (const Decimal &a, double x);
Decimal & operator *= (double x);
Decimal & operator /= (double x);
private:
static const int len = PREC / 9 + 1;
static const int mo = 1000000000;
static void append_to_string(std::string &s, long long x);
bool is_neg;
long long integer;
int data[len];
void init_zero();
void init(const char *s);
};
Decimal::Decimal() {
this->init_zero();
}
Decimal::Decimal(const char *s) {
this->init(s);
}
Decimal::Decimal(const std::string &s) {
this->init(s.c_str());
}
Decimal::Decimal(int x) {
this->init_zero();
if (x < 0) {
is_neg = true;
x = -x;
}
integer = x;
}
Decimal::Decimal(long long x) {
this->init_zero();
if (x < 0) {
is_neg = true;
x = -x;
}
integer = x;
}
Decimal::Decimal(double x) {
this->init_zero();
if (x < 0) {
is_neg = true;
x = -x;
}
integer = (long long)x;
x -= integer;
for (int i = 0; i < len; i++) {
x *= mo;
if (x < 0) x = 0;
data[i] = (int)x;
x -= data[i];
}
}
void Decimal::init_zero() {
is_neg = false;
integer = 0;
memset(data, 0, len * sizeof(int));
}
bool Decimal::is_zero() const {
if (integer) return false;
for (int i = 0; i < len; i++) {
if (data[i]) return false;
}
return true;
}
void Decimal::init(const char *s) {
this->init_zero();
is_neg = false;
integer = 0;
// find the first digit or the negative sign
while (*s != 0) {
if (*s == ‘-‘) {
is_neg = true;
++s;
break;
} else if (*s >= 48 && *s <= 57) {
break;
}
++s;
}
// read the integer part
while (*s >= 48 && *s <= 57) {
integer = integer * 10 + *s - 48;
++s;
}
// read the decimal part
if (*s == ‘.‘) {
int pos = 0;
int x = mo / 10;
++s;
while (pos < len && *s >= 48 && *s <= 57) {
data[pos] += (*s - 48) * x;
++s;
x /= 10;
if (x == 0) {
++pos;
x = mo / 10;
}
}
}
}
void Decimal::append_to_string(std::string &s, long long x) {
if (x == 0) {
s.append(1, 48);
return;
}
char _[30];
int cnt = 0;
while (x) {
_[cnt++] = x % 10;
x /= 10;
}
while (cnt--) {
s.append(1, _[cnt] + 48);
}
}
std::string Decimal::to_string(int p) const {
std::string ret;
if (is_neg && !this->is_zero()) {
ret = "-";
}
append_to_string(ret, this->integer);
ret.append(1, ‘.‘);
for (int i = 0; i < len; i++) {
// append data[i] as "%09d"
int x = mo / 10;
int tmp = data[i];
while (x) {
ret.append(1, 48 + tmp / x);
tmp %= x;
x /= 10;
if (--p == 0) {
break;
}
}
if (p == 0) break;
}
if (p > 0) {
ret.append(p, ‘0‘);
}
return ret;
}
double Decimal::to_double() const {
double ret = integer;
double k = 1.0;
for (int i = 0; i < len; i++) {
k /= mo;
ret += k * data[i];
}
if (is_neg) {
ret = -ret;
}
return ret;
}
bool operator < (const Decimal &a, const Decimal &b) {
if (a.is_neg != b.is_neg) {
return a.is_neg && (!a.is_zero() || !b.is_zero());
} else if (!a.is_neg) {
// a, b >= 0
if (a.integer != b.integer) {
return a.integer < b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] < b.data[i];
}
}
return false;
} else {
// a, b <= 0
if (a.integer != b.integer) {
return a.integer > b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] > b.data[i];
}
}
return false;
}
}
bool operator > (const Decimal &a, const Decimal &b) {
if (a.is_neg != b.is_neg) {
return !a.is_neg && (!a.is_zero() || !b.is_zero());
} else if (!a.is_neg) {
// a, b >= 0
if (a.integer != b.integer) {
return a.integer > b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] > b.data[i];
}
}
return false;
} else {
// a, b <= 0
if (a.integer != b.integer) {
return a.integer < b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] < b.data[i];
}
}
return false;
}
}
bool operator <= (const Decimal &a, const Decimal &b) {
if (a.is_neg != b.is_neg) {
return a.is_neg || (a.is_zero() && b.is_zero());
} else if (!a.is_neg) {
// a, b >= 0
if (a.integer != b.integer) {
return a.integer < b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] < b.data[i];
}
}
return true;
} else {
// a, b <= 0
if (a.integer != b.integer) {
return a.integer > b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] > b.data[i];
}
}
return true;
}
}
bool operator >= (const Decimal &a, const Decimal &b) {
if (a.is_neg != b.is_neg) {
return !a.is_neg || (a.is_zero() && b.is_zero());
} else if (!a.is_neg) {
// a, b >= 0
if (a.integer != b.integer) {
return a.integer > b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] > b.data[i];
}
}
return true;
} else {
// a, b <= 0
if (a.integer != b.integer) {
return a.integer < b.integer;
}
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) {
return a.data[i] < b.data[i];
}
}
return true;
}
}
bool operator == (const Decimal &a, const Decimal &b) {
if (a.is_zero() && b.is_zero()) return true;
if (a.is_neg != b.is_neg) return false;
if (a.integer != b.integer) return false;
for (int i = 0; i < Decimal::len; i++) {
if (a.data[i] != b.data[i]) return false;
}
return true;
}
bool operator != (const Decimal &a, const Decimal &b) {
return !(a == b);
}
Decimal & Decimal::operator += (long long x) {
if (!is_neg) {
if (integer + x >= 0) {
integer += x;
} else {
bool last = false;
for (int i = len - 1; i >= 0; i--) {
if (last || data[i]) {
data[i] = mo - data[i] - last;
last = true;
} else {
last = false;
}
}
integer = -x - integer - last;
is_neg = true;
}
} else {
if (integer - x >= 0) {
integer -= x;
} else {
bool last = false;
for (int i = len - 1; i >= 0; i--) {
if (last || data[i]) {
data[i] = mo - data[i] - last;
last = true;
} else {
last = false;
}
}
integer = x - integer - last;
is_neg = false;
}
}
return *this;
}
Decimal & Decimal::operator += (int x) {
return *this += (long long)x;
}
Decimal & Decimal::operator -= (int x) {
return *this += (long long)-x;
}
Decimal & Decimal::operator -= (long long x) {
return *this += -x;
}
Decimal & Decimal::operator /= (int x) {
if (x < 0) {
is_neg ^= 1;
x = -x;
}
int last = integer % x;
integer /= x;
for (int i = 0; i < len; i++) {
long long tmp = 1LL * last * mo + data[i];
data[i] = tmp / x;
last = tmp - 1LL * data[i] * x;
}
if (is_neg && integer == 0) {
int i;
for (i = 0; i < len; i++) {
if (data[i] != 0) {
break;
}
}
if (i == len) {
is_neg = false;
}
}
return *this;
}
Decimal & Decimal::operator *= (int x) {
if (x < 0) {
is_neg ^= 1;
x = -x;
} else if (x == 0) {
init_zero();
return *this;
}
int last = 0;
for (int i = len - 1; i >= 0; i--) {
long long tmp = 1LL * data[i] * x + last;
last = tmp / mo;
data[i] = tmp - 1LL * last * mo;
}
integer = integer * x + last;
return *this;
}
Decimal operator - (const Decimal &a) {
Decimal ret = a;
// -0 = 0
if (!ret.is_neg && ret.integer == 0) {
int i;
for (i = 0; i < Decimal::len; i++) {
if (ret.data[i] != 0) break;
}
if (i < Decimal::len) {
ret.is_neg = true;
}
} else {
ret.is_neg ^= 1;
}
return ret;
}
Decimal operator + (const Decimal &a, int x) {
Decimal ret = a;
return ret += x;
}
Decimal operator + (int x, const Decimal &a) {
Decimal ret = a;
return ret += x;
}
Decimal operator + (const Decimal &a, long long x) {
Decimal ret = a;
return ret += x;
}
Decimal operator + (long long x, const Decimal &a) {
Decimal ret = a;
return ret += x;
}
Decimal operator - (const Decimal &a, int x) {
Decimal ret = a;
return ret -= x;
}
Decimal operator - (int x, const Decimal &a) {
return -(a - x);
}
Decimal operator - (const Decimal &a, long long x) {
Decimal ret = a;
return ret -= x;
}
Decimal operator - (long long x, const Decimal &a) {
return -(a - x);
}
Decimal operator * (const Decimal &a, int x) {
Decimal ret = a;
return ret *= x;
}
Decimal operator * (int x, const Decimal &a) {
Decimal ret = a;
return ret *= x;
}
Decimal operator / (const Decimal &a, int x) {
Decimal ret = a;
return ret /= x;
}
Decimal operator + (const Decimal &a, const Decimal &b) {
if (a.is_neg == b.is_neg) {
Decimal ret = a;
bool last = false;
for (int i = Decimal::len - 1; i >= 0; i--) {
ret.data[i] += b.data[i] + last;
if (ret.data[i] >= Decimal::mo) {
ret.data[i] -= Decimal::mo;
last = true;
} else {
last = false;
}
}
ret.integer += b.integer + last;
return ret;
} else if (!a.is_neg) {
// a - |b|
return a - -b;
} else {
// b - |a|
return b - -a;
}
}
Decimal operator - (const Decimal &a, const Decimal &b) {
if (!a.is_neg && !b.is_neg) {
if (a >= b) {
Decimal ret = a;
bool last = false;
for (int i = Decimal::len - 1; i >= 0; i--) {
ret.data[i] -= b.data[i] + last;
if (ret.data[i] < 0) {
ret.data[i] += Decimal::mo;
last = true;
} else {
last = false;
}
}
ret.integer -= b.integer + last;
return ret;
} else {
Decimal ret = b;
bool last = false;
for (int i = Decimal::len - 1; i >= 0; i--) {
ret.data[i] -= a.data[i] + last;
if (ret.data[i] < 0) {
ret.data[i] += Decimal::mo;
last = true;
} else {
last = false;
}
}
ret.integer -= a.integer + last;
ret.is_neg = true;
return ret;
}
} else if (a.is_neg && b.is_neg) {
// a - b = (-b) - (-a)
return -b - -a;
} else if (a.is_neg) {
// -|a| - b
return -(-a + b);
} else {
// a - -|b|
return a + -b;
}
}
Decimal operator + (const Decimal &a, double x) {
return a + Decimal(x);
}
Decimal operator + (double x, const Decimal &a) {
return Decimal(x) + a;
}
Decimal operator - (const Decimal &a, double x) {
return a - Decimal(x);
}
Decimal operator - (double x, const Decimal &a) {
return Decimal(x) - a;
}
Decimal & Decimal::operator += (double x) {
*this = *this + Decimal(x);
return *this;
}
Decimal & Decimal::operator -= (double x) {
*this = *this - Decimal(x);
return *this;
}
Decimal & Decimal::operator += (const Decimal &b) {
*this = *this + b;
return *this;
}
Decimal & Decimal::operator -= (const Decimal &b) {
*this = *this - b;
return *this;
}
// ---------- decimal lib end ----------
int read() {
int x = 0, f = 1; char c = getchar();
while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = getchar(); }
while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = getchar(); }
return x * f;
}
#define maxn 8010
int n, K, P, A[maxn], S[maxn];
struct Vec {
int x; Decimal y;
Vec() {}
Vec(int _, Decimal __): x(_), y(__) {}
Vec operator - (const Vec& t) const { return Vec(x - t.x, y - t.y); }
Decimal operator ^ (const Vec& t) const { return x * t.y - y * t.x; }
} ps[maxn];
Decimal f[2][maxn];
int q[maxn], hd, tl;
void solve() {
Decimal ans = A[1];
for(int i = 1; i <= n; i++) f[0][i] = A[1];
bool cur = 1;
for(int j = 1; j <= std::min(K, 8); j++, cur ^= 1) {
hd = 1; tl = 0;
for(int i = j; i <= n; i++) {
ps[i] = Vec(i - 1, S[i] - f[cur^1][i]);
while(hd < tl && (ps[i] - ps[q[tl]] ^ ps[i] - ps[q[tl-1]]) >= 0) tl--;
q[++tl] = i;
Vec p(i, S[i]);
while(hd < tl && (p - ps[q[hd]] ^ p - ps[q[hd+1]]) >= 0) hd++;
p = p - ps[q[hd]]; f[cur][i] = p.y / p.x;
// if(i - q[hd] != 1) printf("f(%d, %d) --> f(%d, %d)\n", j - 1, q[hd], j, i);
}
}
if(K > 8) {
ans = f[cur^1][n-K+8];
for(int i = n - K + 9; i <= n; i++) ans = (ans + A[i]) / 2;
}
else ans = f[cur^1][n];
std::cout << ans.to_string(P << 1) << std::endl;
return ;
}
int main() {
n = read(); K = read(); P = read();
for(int i = 1; i <= n; i++) A[i] = read();
int t = n; n = 1;
for(int i = 2; i <= t; i++) if(A[i] > A[1]) A[++n] = A[i];
K = std::min(K, n - 1);
std::sort(A + 2, A + n + 1);
for(int i = 1; i <= n; i++) S[i] = S[i-1] + A[i];
solve();
return 0;
}
[UOJ#223][BZOJ4654][Noi2016]国王饮水记
标签：long app append 影响 不能 number 含义 nbsp log
原文地址：http://www.cnblogs.com/xiao-ju-ruo-xjr/p/7100632.html
