Bzoj 1029: [JSOI2007] Construction repair (greed)

Sort by T2 then greedy ...

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#include <cstdio>#include <cstring>#include <algorithm>#include <queue>using namespace std;const int MAXN = 150009;struct O {int t1, T2;void Read () {scanf ("%d%d", &t1, &t2);}BOOL Operator < (const O &o) Const {return T2 < o.t2;}} O[MAXN];int N;priority_queue<int> Q;void init () {scanf ("%d", &n);for (int i = 0; i < N; i++) o[i]. Read ();} void Solve () {sort (o, O + N);int cnt = 0, ans = 0;for (int i = 0; i < N; i++) {if (cnt + o[i].t1 <= o[i].t2)cnt + = O[i].t1, Q.push (O[I].T1), ans++;else {int x = Q.top ();if (x > O[i].t1 && cnt-x + o[i].t1 <= o[i].t2)Q.pop (), Q.push (O[I].T1), cnt + = O[i].t1-x;}}printf ("%d\n", ans);} int main () {init ();solve ();return 0;}

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1029: [JSOI2007] Construction repair time limit: 4 Sec Memory Limit: 162 MB
Submit: 3033 Solved: 1355
[Submit] [Status] [Discuss] Description

Xiao Gang is playing a computer game called "Building Repair" provided by Jsoi: After a fierce battle, the T tribe destroyed all the invaders of the Z tribe. But there are already n construction facilities in the T tribe's base that have been severely damaged, and if not repaired soon, the construction facilities will be completely destroyed. Now the situation is: there is only one repairman at the base of the T tribe, although he can get to any building in an instant, but repairing each building will take some time. At the same time, the repairman repaired a building to repair the next building, unable to repair multiple buildings at the same time. If a building has not been completely repaired for a period of time, the building will be scrapped. Your mission is to help small just make a reasonable order of repairs to repair as many buildings as possible.

Input

The first line is an integer n, and the next n rows of two integers per line t1,t2 describe a building: it takes T1 seconds to repair the building, and if it is not repaired within T2 seconds, the building is scrapped.

Output

Output an integer s, which means that a maximum of s buildings can be repaired. N < 150,000; T1 < T2 < Maxlongint

Sample Input4
100 200
200 1300
1000 1250
3200Sample Output3HINT

Source

Bzoj 1029: [JSOI2007] Construction repair (greed)