제출 #677838

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
677838		qwerasdfzxcl	Seesaw (JOI22_seesaw)	C++17	0 / 100	1 ms	340 KiB

seesaw

#include <bits/stdc++.h>

typedef long long ll;
using namespace std;
int dx[4] = {1, -1, 0, 0}, dy[4] = {0, 0, 1, -1};

struct DSU{
    int path[4004000], chk[4004000], n;
    vector<int> buf;
    void init(int _n){
        n = _n;
        for (int i=0;i<n*n;i++) path[i] = i, chk[i] = 0;
    }
    int find(int s){
        if (s==path[s]) return s;
        return path[s] = find(path[s]);
    }
    void merge(int s, int v){
        if (!chk[s] || !chk[v]) return;
        s = find(s), v = find(v);
        if (s==v) return;
        path[s] = v;
    }
    void on(int x, int y){
        int pos = (x-1)*n + y-1;

        if (x==y) pos = 0;

        chk[pos] = 1;
        buf.push_back(pos);

        for (int k=0;k<4;k++){
            int nx = x + dx[k], ny = y + dy[k];
            if (nx<=0 || nx>n || ny<=0 || ny>n || nx>ny) continue;
            int np = (nx-1)*n + ny-1;
            merge(pos, np);
        }
    }
    void off(){for (auto &x:buf){path[x] = x; chk[x] = 0;} buf.clear();}
    bool ok(){return find(0) == find(n-1) && chk[0] && chk[n-1];}
}dsu;

struct Frac{
    ll a, b;
    Frac(){}
    Frac(ll _a, ll _b): a(_a), b(_b) {}

    long double ch(){return (long double) a / b;}

    bool operator < (const Frac &F) const{
        return (__int128)a * F.b < (__int128)b * F.a;
    }
}val[2020][2020];
vector<pair<int, int>> P;
int a[2020];

bool cmp (const pair<int, int> &x, const pair<int, int> &y){
    return val[x.first][x.second] < val[y.first][y.second];
}

int main(){
    int n;
    scanf("%d", &n);
    for (int i=1;i<=n;i++) scanf("%d", a+i);

    for (int i=1;i<=n;i++){
        val[i][i] = Frac(a[i], 1);
        P.emplace_back(i, i);
        for (int j=i+1;j<=n;j++){
            val[i][j].a = val[i][j-1].a + a[j];
            val[i][j].b = j-i+1;
            P.emplace_back(i, j);
            //printf("%Lf ", val[i][j].ch());
        }
        //printf("\n");
    }

    sort(P.begin(), P.end(), cmp);
    //for (int i=0;i<(int)P.size()-1;i++) assert(!(val[P[i+1].first][P[i+1].second] < val[P[i].first][P[i].second]));
    long double ans = 1e18;
    dsu.init(n);

    for (int l=0;l<(int)P.size();l++){
        //printf("Start = %d %d (%Lf)\n", P[l].first, P[l].second, val[P[l].first][P[l].second].ch());
        int r;
        for (r=l;r<(int)P.size();r++){
            //printf(" %d %d (%Lf)\n", P[r].first, P[r].second, val[P[r].first][P[r].second].ch());
            dsu.on(P[r].first, P[r].second);
            if (dsu.ok()){
                //printf("ok %Lf\n", val[P[r].first][P[r].second].ch() - val[P[l].first][P[l].second].ch());
                ans = min(ans, val[P[r].first][P[r].second].ch() - val[P[l].first][P[l].second].ch());
                break;
            }
        }

        if (r==(int)P.size()) break;

        dsu.off();
        dsu.init(n);
    }

    printf("%.15Lf\n", ans);
    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

seesaw.cpp: In function 'int main()':
seesaw.cpp:63:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   63 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
seesaw.cpp:64:33: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     for (int i=1;i<=n;i++) scanf("%d", a+i);
      |                            ~~~~~^~~~~~~~~~~

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