MINROAD - VOI 2014 - Con đường Tùng Trúc

Tác giả: RR

Ngôn ngữ: C++

#include <bits/stdc++.h>

#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 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;
const int BUFSIZE = (1<<12) + 17;
char BUF[BUFSIZE+1], *inp=BUF;
#define GETCHAR(INP) { \
    if(!*inp && !REACHEOF) { \
        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 int MN = 300111;
const int oo = 1000111000;

int n, a, b, c1[MN], c2[MN];
pair<int,int> x[MN];

int main() {
    ios :: sync_with_stdio(false);
    cin >> n >> a >> b;
    FOR(i,1,n) cin >> x[i].first >> x[i].second;
    sort(x+1, x+n+1);
    FOR(i,1,n) {
        c1[i] = c1[i-1] + (x[i].second == 1);
        c2[i] = c2[i-1] + (x[i].second == 2);
    }
    int best = oo;
    FOR(i,1,n) {
        if (c1[i] < a || c2[i] < b) continue;
        int left = 1, right = i, res = 1;
        while (left <= right) {
            int mid = (left + right) >> 1;
            if (c1[i] - c1[mid-1] >= a && c2[i] - c2[mid-1] >= b) {
                res = mid;
                left = mid + 1;
            }
            else right = mid - 1;
        }
        best = min(best, x[i].first - x[res].first);
    }
    if (best == oo) cout << -1; else cout << best;
    cout << endl;
    return 0;
}

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