Submission #1818757

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Source Code Expand

#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
using namespace std;

#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define ALL(c) (c).begin(), (c).end()

typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VI> VVI;
typedef vector<VL> VVL;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

const ll INF = 1e17;

struct SegmentTree{
    const ll INF = 1e17;
    int n, width;
    VL dat;

    void init(int x){
        n = x;
        width = 1;
        while (width < n) width *= 2;
        dat.resize(2*width-1);
        REP(i,2*width-1) dat[i] = INF;
    }

    void update(int i, ll x){
        i += width - 1;
        dat[i] = x;
        while (i > 0){
            i = (i - 1) / 2;
            dat[i] = min(dat[i*2+1], dat[i*2+2]);
        }
    }

    ll query(int a, int b, int k, int l, int r){
        if (r <= a || b <= l) return INF;
        if (a <= l && r <= b) return dat[k];
        ll vl = query(a, b, k*2+1, l, (l+r)/2);
        ll vr = query(a, b, k*2+2, (l+r)/2, r);
        return min(vl, vr);
    }

    // [l, r)
    ll query(int l, int r){
        return query(l, r, 0, 0, width);
    }
};

int main() {
    int n, m;
    cin >> n >> m;
    VL a(n);
    REP(i,n) scanf("%lld", &a[i]);
    VL s(n+1);
    REP(i,n) s[i+1] = s[i] + a[i];

    vector<PL> p(n+1);
    REP(i,n+1) p[i] = PL(s[i], i);
    sort(ALL(p));
    VI pos(n+1);
    REP(i,n+1) pos[i] = p[i].second;

    // REP(i,n+1) cout << s[i] << " ";
    // cout << endl;
    // REP(i,n+1) cout << pos[i] << " ";
    // cout << endl;

    VVL dp(n+1, VL(m, INF));
    dp[0][0] = 0;

    SegmentTree sg1, sg2;
    REP(k,m){
        sg1.init(n+1);
        sg2.init(n+1);
        REP(i,n+1) sg1.update(i, dp[i][k] + s[i]);
        // REP(i,n+1) cout << sg1.query(i, i+1) << " ";
        // cout << endl;
        REP(i,n+1){
            // REP(j,n+1) cout << sg1.query(j, j+1) << " ";
            // cout << endl;
            // REP(j,n+1) cout << sg2.query(j, j+1) << " ";
            // cout << endl << endl;
            int p = pos[i];
            // cout << p << endl;
            dp[p][k+1] = min(sg1.query(0, p) - s[p], sg2.query(0, p) + s[p]);
            sg1.update(p, INF);
            sg2.update(p, dp[p][k] - s[p]);
        }
    }

    // cout << endl;
    // REP(k,m+1){
    //     REP(i,n+1) cout << dp[i][k] << " ";
    //     cout << endl;
    // }

    cout << dp[n][m] << endl;

    return 0;
}

Submission Info

Judge Result