Codeforces Round #336(Div.2) (1/5) (Div.1) (0/5)

maksyuki 发表于比赛分类，标签: 比赛-codeforces

26 12月 2015

A Saitama Destroys Hotel

Saitama accidentally destroyed a hotel again. To repay the hotel company, Genos has volunteered to operate an elevator in one of its other hotels. The elevator is special — it starts on the top floor, can only move down, and has infinite capacity. Floors are numbered from 0 to s and elevator initially starts on floor s at time 0.

The elevator takes exactly 1 second to move down exactly 1 floor and negligible time to pick up passengers. Genos is given a list detailing when and on which floor passengers arrive. Please determine how long in seconds it will take Genos to bring all passengers to floor 0.

Input

The first line of input contains two integers n and s (1 ≤ n ≤ 100, 1 ≤ s ≤ 1000) — the number of passengers and the number of the top floor respectively.

The next n lines each contain two space-separated integers f_i and t_i (1 ≤ f_i ≤ s, 1 ≤ t_i ≤ 1000) — the floor and the time of arrival in seconds for the passenger number i.

Output

Print a single integer — the minimum amount of time in seconds needed to bring all the passengers to floor 0.

Sample test(s)

input

3 7
2 1
3 8
5 2

output

input

5 10
2 77
3 33
8 21
9 12
10 64

output

Note

In the first sample, it takes at least 11 seconds to bring all passengers to floor 0. Here is how this could be done:

Move to floor 5: takes 2seconds.
Pick up passenger 3.
Move to floor 3: takes 2seconds.
Wait for passenger 2to arrive: takes 4seconds.
Pick up passenger 2.
Go to floor 2: takes 1second.
Pick up passenger 1.
Go to floor 0: takes 2seconds.

This gives a total of 2 + 2 + 4 + 1 + 2 = 11 seconds.

题目类型：简单模拟

算法分析：先按照楼层排序，最后从上到下模拟计算即可

/*************************************************
Author        :supermaker
Created Time  :2015/12/24 0:11:13
File Location :C:\Users\abcd\Desktop\TheEternalPoet
**************************************************/

#pragma comment(linker, "/STACK:102400000,102400000")
#include <set>
#include <bitset>
#include <list>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <string>
#include <vector>
#include <ios>
#include <iostream>
#include <fstream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <utility>
#include <complex>
#include <numeric>
#include <functional>
#include <cmath>
#include <ctime>
#include <climits>
#include <cstdarg>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cassert>
using namespace std;

#define CFF freopen ("aaa.txt", "r", stdin)
#define CPPFF ifstream cin ("aaa.txt")
#define DB(ccc) cout << #ccc << " = " << ccc << endl
#define PB push_back
#define MP(A, B) make_pair(A, B)

typedef long long LL;
typedef unsigned long long ULL;
typedef double DB;
typedef pair <int, int> PII;
typedef pair <int, bool> PIB;

const int INF = 0x7F7F7F7F;
const int MOD = 1e9 + 7;
const double EPS = 1e-10;
const double PI = 2 * acos (0.0);
const int maxn = 1e5 + 6666;

struct node
{
    int a, b;
};

bool operator < (const node &a, const node &b)
{
    return a.a < b.a;
};

node aa[maxn];

int main()
{
    //CFF;
    //CPPFF;        
    int n, s;
    while (scanf ("%d%d", &n, &s) != EOF)
    {
        for (int i = 1; i <= n; i++)
            scanf ("%d%d", &aa[i].a, &aa[i].b);

        sort (aa + 1, aa + 1 + n);
        LL res = 0, tt = 0;
        aa[n+1].a = s, aa[n+1].b = 0;
        aa[0].a = 0, aa[0].b = 0;
        for (int i = n + 1; i >= 1; i--)
        {
            res += aa[i].a - aa[i-1].a;
            tt += aa[i].a - aa[i-1].a;
            if (tt < aa[i-1].b)
            {   
                res += aa[i-1].b - tt;
                int ta = aa[i-1].b - tt;
                tt += ta;
            }
        }
        printf ("%I64d\n", res);
    }
    return 0;
}

/*************************************************

Author :supermaker

Created Time :2015/12/24 0:11:13

File Location :C:\Users\abcd\Desktop\TheEternalPoet

**************************************************/

#pragma comment(linker, "/STACK:102400000,102400000")

#include <set>

#include <bitset>

#include <list>

#include <map>

#include <stack>

#include <queue>

#include <deque>

#include <string>

#include <vector>

#include <ios>

#include <iostream>

#include <fstream>

#include <sstream>

#include <iomanip>

#include <algorithm>

#include <utility>

#include <complex>

#include <numeric>

#include <functional>

#include <cmath>

#include <ctime>

#include <climits>

#include <cstdarg>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <cctype>

#include <cassert>

using namespace std;

#define CFF freopen ("aaa.txt", "r", stdin)

#define CPPFF ifstream cin ("aaa.txt")

#define DB(ccc) cout << #ccc << " = " << ccc << endl

#define PB push_back

#define MP(A, B) make_pair(A, B)

typedef long long LL;

typedef unsigned long long ULL;

typedef double DB;

typedef pair <int, int> PII;

typedef pair <int, bool> PIB;

const int INF = 0x7F7F7F7F;

const int MOD = 1e9 + 7;

const double EPS = 1e-10;

const double PI = 2 * acos (0.0);

const int maxn = 1e5 + 6666;

struct node

{

int a, b;

};

bool operator < (const node &a, const node &b)

{

return a.a < b.a;

};

node aa[maxn];

int main()

{

//CFF;

//CPPFF;

int n, s;

while (scanf ("%d%d", &n, &s) != EOF)

{

for (int i = 1; i <= n; i++)

scanf ("%d%d", &aa[i].a, &aa[i].b);

sort (aa + 1, aa + 1 + n);

LL res = 0, tt = 0;

aa[n+1].a = s, aa[n+1].b = 0;

aa[0].a = 0, aa[0].b = 0;

for (int i = n + 1; i >= 1; i--)

{

res += aa[i].a - aa[i-1].a;

tt += aa[i].a - aa[i-1].a;

if (tt < aa[i-1].b)

{

res += aa[i-1].b - tt;

int ta = aa[i-1].b - tt;

tt += ta;

}

printf ("%I64d\n", res);

}

return 0;

}

TopCoder SRM#676(Div2)(2/3)

BestCoder Round #67 (2/4)

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Codeforces Round #336(Div.2) (1/5) (Div.1) (0/5)

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