MOVE12 - VOI 2012 Điều động

Tác giả: RR

Ngôn ngữ: C++

#include <sstream>
#include <iomanip>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <string>
#include <deque>
#include <complex>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define FORN(i,a,b) for(int i=(a),_b=(b);i<_b;i++)
#define DOWN(i,a,b) for(int i=a,_b=(b);i>=_b;i--)
#define SET(a,v) memset(a,v,sizeof(a))
#define sqr(x) ((x)*(x))
#define ll long long
#define F first
#define S second
#define PB push_back
#define MP make_pair

#define DEBUG(x) cout << #x << " = "; cout << x << endl;
#define PR(a,n) cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl;
#define PR0(a,n) cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl;
using namespace std;

//Buffer reading
int INP,AM,REACHEOF;
#define BUFSIZE (1<<12)
char BUF[BUFSIZE+1], *inp=BUF;
#define GETCHAR(INP) { \
    if(!*inp) { \
        if (REACHEOF) return 0;\
        memset(BUF,0,sizeof BUF);\
        int inpzzz = fread(BUF,1,BUFSIZE,stdin);\
        if (inpzzz != BUFSIZE) REACHEOF = true;\
        inp=BUF; \
    } \
    INP=*inp++; \
}
#define DIG(a) (((a)>='0')&&((a)<='9'))
#define GN(j) { \
    AM=0;\
    GETCHAR(INP); while(!DIG(INP) && INP!='-') GETCHAR(INP);\
    if (INP=='-') {AM=1;GETCHAR(INP);} \
    j=INP-'0'; GETCHAR(INP); \
    while(DIG(INP)){j=10*j+(INP-'0');GETCHAR(INP);} \
    if (AM) j=-j;\
}
//End of buffer reading

const long double PI = acos((long double) -1.0);
const int MN = 100111;

int n, x[MN], t[MN];
pair<int,int> a[MN];
multiset< pair<int,int> > s;

bool check(int v) {
    FOR(i,1,n) {
        int can = v / t[i];
        a[i] = MP(max(x[i] - can, 1), min(x[i] + can, n));
    }
    sort(a+1, a+n+1);
    s.clear();

    int j = 0;
    FOR(i,1,n) {
        while (j < n && a[j+1].F <= i) {
            ++j;
            s.insert(MP(a[j].S, a[j].F));
        }
        if (s.empty()) return false;
        pair<int,int> cur = *s.begin(); s.erase(s.begin());

        if (cur.F < i) return false;
    }
    return true;
}

int main() {
    scanf("%d", &n);
    FOR(i,1,n) scanf("%d%d", &x[i], &t[i]);

    int l = 0, r = 1000111000, res = r;
    while (l <= r) {
        int mid = (l + r) >> 1;
        if (check(mid)) {
            res = mid;
            r = mid - 1;
        }
        else l = mid + 1;
    }
    cout << res << endl;
    return 0;
}

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