codeforces248(div1) A. Ryouko's Memory Note

可以把序列中一个数改变，使得序列中后一个数与前一个数差的绝对值之和最小

把与数x相邻的数加入G[x]的链表中(若这个数值也为x，则不加入)   那么改变了数x，则相当于只会影响到这个链表中的数

为了让x变化后的数  与这个链表中的数差值绝对值之和最小   取排序后的序列的中位数即可

//#pragma comment(linker, "/STACK:102400000,102400000")//HEAD#include <cstdio>#include <cstring>#include <vector>#include <iostream>#include <algorithm>#include <queue>#include <string>#include <set>#include <stack>#include <map>#include <cmath>#include <cstdlib>#include <list>using namespace std;//LOOP#define FE(i, a, b) for(int i = (a); i <= (b); ++i)#define FED(i, b, a) for(int i = (b); i>= (a); --i)#define REP(i, N) for(int i = 0; i < (N); ++i)#define CLR(A,value) memset(A,value,sizeof(A))//STL#define PB push_back//INPUT#define RI(n) scanf("%d", &n)#define RII(n, m) scanf("%d%d", &n, &m)#define RIII(n, m, k) scanf("%d%d%d", &n, &m, &k)#define RS(s) scanf("%s", s)#define FF(i, a, b) for(int i = (a); i < (b); ++i)#define FD(i, b, a) for(int i = (b) - 1; i >= (a); --i)#define CPY(a, b) memcpy(a, b, sizeof(a))#define FC(it, c) for(__typeof((c).begin()) it = (c).begin(); it != (c).end(); it++)#define EQ(a, b) (fabs((a) - (b)) <= 1e-10)#define ALL(c) (c).begin(), (c).end()#define SZ(V) (int)V.size()#define RIV(n, m, k, p) scanf("%d%d%d%d", &n, &m, &k, &p)#define RV(n, m, k, p, q) scanf("%d%d%d%d%d", &n, &m, &k, &p, &q)#define WI(n) printf("%d\n", n)#define WS(s) printf("%s\n", s)#define sqr(x) x * xtypedef vector <int> VI;typedef unsigned long long ULL;typedef long long LL;const int INF = 0x3f3f3f3f;const int maxn = 100010;const double eps = 1e-10;const LL MOD = 1e9 + 9;int a[maxn];VI G[maxn];int main(){    int n, m;    while (~RII(n, m))    {        REP(i, n + 1)   G[i].clear();        FE(i, 1, m)           RI(a[i]);        LL tot = 0;        FE(i, 1, m)        {            if (i != 1 && a[i] != a[i - 1])                G[a[i]].push_back(a[i - 1]);            if (i != m && a[i] != a[i + 1])                G[a[i]].push_back(a[i + 1]), tot += abs(a[i + 1] - a[i]);        }        LL ans = tot;//        cout << tot << "----" <<endl;        FE(i, 1, n)        {            if (G[i].size() == 0) continue;            LL t = tot;//            cout << t1 << "  ----x:";            sort(G[i].begin(), G[i].end());            int x = G[i][G[i].size() / 2];            REP(j, G[i].size())                t += abs(G[i][j] - x) - abs(G[i][j] - i);            ans = min(ans, t);//            cout << x <<"   t2: " << t2 <<endl;        }//        if (m == 1) ans = 0;        cout << ans << endl;    }    return 0;}/*4 61 2 3 4 3 210 59 4 3 8 81000 50 1 1000 999 1*/