CF981F Round Marriage

这道题其实可以用暴力水过qwq

首先可以知道一个暴力做法如下，具体地来说可以用调整法证明其正确性，但是过不了所有的点。

#pragma GCC optimize (2)
#pragma G++ optimize (2)
#include <algorithm>
#include <cstdio>
#include <iostream>
#include <vector>
#define MAXN 200005
using namespace std;
int A[MAXN], B[MAXN];
int l;;
inline int read(){int x=0,f=1;char ch=getchar();while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}while (ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}return x*f;
}
inline int max(int a, int b)
{return a > b ? a : b;
}
inline int min(int a, int b)
{return a < b ? a : b;
}
inline int calc(int a, int b)
{int dis = a > b ? a - b : b - a;return min(dis, l - dis);
}
int num1[MAXN],num2[MAXN];
int main()
{int n;n=read(),l=read();for (register int i = 0; i < n; ++i){A[i]=read();}for (register int i = 0; i < n; ++i){B[i]=read();}sort(A, A + n);sort(B, B + n);int minmax = 0x7fffffff;for (register int i = 0; i <n; ++i){int maxn = -0x7fffffff;for (register int j = 0; j <n; ++j){maxn = max(maxn, calc(A[j], B[(i + j >= n) ? (i + j - n) : (i + j)]));}minmax = min(minmax, maxn);}printf("%d\n", minmax);return 0;
}

然后，我们有一个比较显然的优化：如果当前最大值已经比最小的最大值要大的话，就break掉。

#pragma GCC optimize (2)
#pragma G++ optimize (2)
#include <algorithm>
#include <cstdio>
#include <iostream>
#include <vector>
#define MAXN 200005
using namespace std;
int A[MAXN], B[MAXN];
int l;;
inline int read(){int x=0,f=1;char ch=getchar();while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}while (ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}return x*f;
}
inline int max(int a, int b)
{return a > b ? a : b;
}
inline int min(int a, int b)
{return a < b ? a : b;
}
inline int calc(int a, int b)
{int dis = a > b ? a - b : b - a;return min(dis, l - dis);
}
int num1[MAXN],num2[MAXN];
int main()
{int n;n=read(),l=read();for (register int i = 0; i < n; ++i){A[i]=read();}for (register int i = 0; i < n; ++i){B[i]=read();}sort(A, A + n);sort(B, B + n);int minmax = 0x7fffffff;for (register int i = 0; i <n; ++i){int maxn = -0x7fffffff;for (register int j = 0; j <n; ++j){maxn = max(maxn, calc(A[j], B[(i + j >= n) ? (i + j - n) : (i + j)]));if (maxn >= minmax){break;}}minmax = min(minmax, maxn);}printf("%d\n", minmax);return 0;
}

但是，显然这个程序在随机数据下表现良好，但是会被一些特殊数据卡掉。。。比如说这个程序就T在了第24个点

什么？你要写二分？too young too naive！如果数据不是随机的，我们就“构造”出随机的数据，比如说，用random_shuffle优化枚举顺序

#pragma GCC optimize (2)
#pragma G++ optimize (2)
#include <algorithm>
#include <cstdio>
#include <iostream>
#include <vector>
#define MAXN 200005
using namespace std;
int A[MAXN], B[MAXN];
int l;;
inline int read(){int x=0,f=1;char ch=getchar();while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}while (ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}return x*f;
}
inline int max(int a, int b)
{return a > b ? a : b;
}
inline int min(int a, int b)
{return a < b ? a : b;
}
inline int calc(int a, int b)
{int dis = a > b ? a - b : b - a;return min(dis, l - dis);
}
int num1[MAXN],num2[MAXN];
int main()
{int n;n=read(),l=read();for (register int i = 0; i < n; ++i){//scanf("%d", &A[i]);A[i]=read(),num1[i]=i;}for (register int i = 0; i < n; ++i){//scanf("%d", &B[i]);B[i]=read(),num2[i]=i;}random_shuffle(num1,num1+n);random_shuffle(num2,num2+n);sort(A, A + n);sort(B, B + n);int minmax = 0x7fffffff;for (register int ii = 0; ii <n; ++ii){int maxn = -0x7fffffff;for (register int jj = 0; jj <n; ++jj){int i=num1[ii],j=num2[jj];maxn = max(maxn, calc(A[j], B[(i + j >= n) ? (i + j - n) : (i + j)]));if (maxn >= minmax){break;}}minmax = min(minmax, maxn);}printf("%d\n", minmax);return 0;
}

然后就A了 hhh

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