题解报告（CDUT暑期集训——第五场）

题解报告（CDUT暑期集训——第五场）

---

B - Beautiful Now

HDU - 6351

• __思路：直接暴力全排列就行了 最多(10!)次 题目限制2500ms 全排列大概是2000多ms（最开始数组开的20疯狂t 结束前十几秒听到尧神说把数组开小过了就马上改了一交过了（%%尧神 时间卡的太死了（ __

• AC代码

---

#include<stdio.h>
#include<iostream>
#include<math.h>
#include<algorithm>
#include<string.h>
#include<queue>
#include<set>
#include<string>
#include<sstream>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;

ll Pow_mod(ll a, ll b, ll c){
    ll ans = 1;
    a %= c;
    while (b){
        if (b & 1) ans = (ans * a) % c;
        a = (a * a) % c;
        b >>= 1;
    }
    return (ans % c);
}

int gcd(int a, int b){
    return b == 0 ? a : gcd(b, a % b);
}

const int N = 10;
const int M = 20;
const int INF = 0x3f3f3f3f;

int t, k, len, init_val, ans_min, ans_max, cnt, cnt_, sum;
int n_[N], pos[N], vis[N];
char n[M];

void init(){
    init_val = 0;
    len = strlen(n);
    for (int i = 0; i < len; i ++ ){
        n_[i] = (n[i] - '0');
        pos[i] = i;
        init_val = init_val * 10 + n_[i];
    }
    ans_min = init_val;
    ans_max = init_val;
}

bool judge(){
    memset(vis, 0, sizeof(vis));
    cnt = 0;
    for (int i = 0; i < len; i ++ ){
        if (!vis[i]){
            cnt_ = 0;
            while (!vis[i]){
                vis[i] = 1;
                cnt_ ++;
                i = pos[i];
            }
            cnt += (cnt_ - 1);
        }
        if (cnt > k) return false;
    }
    return true;
}

void calc(){
    while (next_permutation(pos, pos + len)){
        if (n_[pos[0]] && judge()){
            sum = 0;
            for (int i = 0; i < len; i ++ )
                sum = sum * 10 + n_[pos[i]];
            ans_min = min(ans_min, sum);
            ans_max = max(ans_max, sum);
        }
    }
}

int main(){
    scanf("%d", &t);
    while (t -- ){
        scanf("%s%d", n, &k);
        init();
        calc();
        printf("%d %d
", ans_min, ans_max);
    }
    return 0;
}

E - Everything Has Changed

HDU - 6354

• 思路：水题 计算几何 画图工具一画就出来了 最开始忘了判断包含的情况调过贡献了一发wa（菜是原罪

• AC代码

---

#include<stdio.h>
#include<iostream>
#include<math.h>
#include<algorithm>
#include<string.h>
#include<queue>
#include<set>
#include<string>
#include<sstream>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;

ll Pow_mod(ll a, ll b, ll c){
    ll ans = 1;
    a %= c;
    while (b){
        if (b & 1) ans = (ans * a) % c;
        a = (a * a) % c;
        b >>= 1;
    }
    return (ans % c);
}

int gcd(int a, int b){
    return b == 0 ? a : gcd(b, a % b);
}

const double pi = acos(-1);

int t, m;
double R, x, y, r, d, ans, alpha, beta;

int main(){
    scanf("%d", &t);
    while (t -- ){
        scanf("%d%lf", &m, &R);
        ans = 2 * pi * R;
        while (m -- ){
            scanf("%lf%lf%lf", &x, &y, &r);
            d = sqrt(x * x + y * y);
            if (d >= R + r) continue;
            else if (d == R - r) ans += 2 * pi * r;
            else if (d > fabs(R - r)){
                alpha = 2 * acos((R * R + d * d - r * r) / (2 * R * d));
                beta = 2 * acos((d * d + r * r - R * R) / (2 * d * r));
                ans += (beta * r - alpha * R);
            }
        }
        printf("%.20lf
", ans);
    }
    return 0;
}