BILL - Hóa đơn tiền điện

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);

long long conv(long long x) {
    long long res = 0;
    res += min(x, 100LL) * 200;
    x -= 100;
    if (x <= 0) return res;

    res += min(x, 10000LL - 100) * 300;
    x -= 10000 - 100;
    if (x <= 0) return res;

    res += min(x, 1000000LL - 10000) * 500;
    x -= 1000000 - 10000;
    if (x <= 0) return res;

    res += x * 700;
    return res;
}

long long rev(long long x) {
    long long res = 0;
    if (x <= 100 * 200) return x / 200;
    res += 100;
    x -= 100 * 200;

    if (x <= (10000 - 100) * 300) return res + x / 300;
    res = 10000;
    x -= (10000 - 100) * 300;

    if (x <= (1000000 - 10000) * 500) return res + x / 500;
    res = 1000000;
    x -= (1000000 - 10000) * 500;

    return x / 700 + res;
}

int main() {
    long long x, y;
    while (cin >> x >> y) {
        long long sum = rev(x);

        FOR(i,1,sum/2) {
            long long a = conv(i);
            long long b = conv(sum-i);

            if (b-a == y) {
                cout << a << endl;
                break;
            }
        }
    }
    return 0;
}

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