HDU 1.3.5 Wooden Sticks

Problem Description

There is a pile of n wooden sticks. The length and weight of each stick are known in advance. The sticks are to be processed by a woodworking machine in one by one fashion. It needs some time, called setup time, for the machine to prepare processing a stick. The setup times are associated with cleaning operations and changing tools and shapes in the machine. The setup times of the woodworking machine are given as follows:

(a) The setup time for the first wooden stick is 1 minute.
(b) Right after processing a stick of length l and weight w , the machine will need no setup time for a stick of length l' and weight w' if l<=l' and w<=w'. Otherwise, it will need 1 minute for setup.

You are to find the minimum setup time to process a given pile of n wooden sticks. For example, if you have five sticks whose pairs of length and weight are (4,9), (5,2), (2,1), (3,5), and (1,4), then the minimum setup time should be 2 minutes since there is a sequence of pairs (1,4), (3,5), (4,9), (2,1), (5,2).

 

Input

The input consists of T test cases. The number of test cases (T) is given in the first line of the input file. Each test case consists of two lines: The first line has an integer n , 1<=n<=5000, that represents the number of wooden sticks in the test case, and the second line contains n 2 positive integers l1, w1, l2, w2, ..., ln, wn, each of magnitude at most 10000 , where li and wi are the length and weight of the i th wooden stick, respectively. The 2n integers are delimited by one or more spaces.

 

Output

The output should contain the minimum setup time in minutes, one per line.

 

Sample Input

3 5 4 9 5 2 2 1 3 5 1 4 3 2 2 1 1 2 2 3 1 3 2 2 3 1

 

Sample Output

213

 

 

Source

Asia 2001, Taejon (South Korea)

 

 

【思路】

把wooden stick按length排序。

不断循环(很多个for，嵌套在while里面)，若下一个stick的length和weight都大于等于前一个处理的stick，那么删掉这个stick。

每一次循环开始时都增加1 min的 preprocess time.

#include<stdio.h>#include"algorithm"using namespace std;struct stick{int length;int weight;bool deleted = false;};int cmp(const stick &a, const stick &b){return a.length < b.length;}int larger(const stick &a, const int l,const int w){return a.length >= l&&a.weight >=w;}stick st[5000];int main(){freopen("f://in.txt", "r", stdin);freopen("f://out.txt", "w", stdout);int testCase;scanf("%d", &testCase);while (testCase--){memset(st, 0, sizeof(st));int stickNum;scanf("%d", &stickNum);for (int i = 0; i < stickNum; i++)scanf("%d%d", &st[i].length, &st[i].weight);sort(st, st + stickNum, cmp);int minTime = 0;int leftAmount = stickNum;while (leftAmount){minTime++;int lastLength = -1, lastWeight = -1;for (int i = 0; i < stickNum ; i++)if (st[i].deleted == false&&larger(st[i], lastLength, lastWeight)){st[i].deleted = true;lastLength = st[i].length;lastWeight = st[i].weight;leftAmount--;}}printf("%d\n", minTime);}return 0;}