Maratones competidas/Maratón Nacional 2011/workspace/e/gas.cpp

   1 // Equipo Poncho, Carriel y Ruana
   2 using namespace std;
   3 #include <algorithm>
   4 #include <iostream>
   5 #include <iterator>
   6 #include <sstream>
   7 #include <fstream>
   8 #include <cassert>
   9 #include <climits>
  10 #include <cstdlib>
  11 #include <cstring>
  12 #include <string>
  13 #include <cstdio>
  14 #include <vector>
  15 #include <cmath>
  16 #include <queue>
  17 #include <stack>
  18 #include <list>
  19 #include <map>
  20 #include <set>
  21
  22 template <class T> string toStr(const T &x)
  23 { stringstream s; s << x; return s.str(); }
  24 template <class T> int toInt(const T &x)
  25 { stringstream s; s << x; int r; s >> r; return r; }
  26
  27 #define For(i, a, b) for (int i=(a); i<(b); ++i)
  28 #define foreach(x, v) for (typeof (v).begin() x = (v).begin(); x != (v).end(); ++x)
  29 #define D(x) cout << #x " = " << (x) << endl;
  30
  31 const double EPS = 1e-9;
  32
  33 int cmp(double x, double y = 0, double tol = EPS) {
  34     return (x <= y + tol) ? (x + tol < y) ? -1 : 0 : 1;
  35 }
  36
  37 #define INPUT_FILE "problemname"
  38
  39
  40 int main(){
  41     freopen(INPUT_FILE ".in", "r", stdin);
  42     long long l, gases;
  43
  44     vector<pair<long long, long long>> stations;
  45
  46     while(cin >> l >> gases) {
  47
  48         stations.clear();
  49         if(l == 0 and gases == 0) break;
  50         for(long long i=0; i<g; i++) {
  51             long long p, r;
  52             cin >> p >> r;
  53             long long li, ls;
  54             li = max(0, p-r);
  55             ls = min(l, p+r);
  56             stations.push_back(make_pair(li, ls);
  57         }
  58         sort(stations.begin(), stations.end());
  59         long long usados = 0;
  60         for(long long i = 0; i<l;) {
  61             long long fin = i;
  62             for(long long g; g<stations.length(); ++g) {
  63                 if (stations[g].first <= i and stations[g].second > i) {
  64                     fin = max(fin, stations[g].second);
  65                 }
  66                 if (stations[g].first > i) break;
  67             }
  68             if(i == fin) {
  69                 cout << -1 << endl;
  70                 break;
  71             }
  72             i = fin;
  73             usados++;
  74         }
  75         cout << gases-usados << endl;
  76
  77     }
  78     return 0;
  79
  80 }