POJ1065-Wooden Sticks

Wooden Sticks

Time Limit: 1000MS Memory Limit: 10000KTotal Submissions: 23228 Accepted: 9979

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 ( 9 , 4 ) , ( 2 , 5 ) , ( 1 , 2 ) , ( 5 , 3 ) , and ( 4 , 1 ) , then the minimum setup time should be 2 minutes since there is a sequence of pairs ( 4 , 1 ) , ( 5 , 3 ) , ( 9 , 4 ) , ( 1 , 2 ) , ( 2 , 5 ) .

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 2n 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

Taejon 2001

题意：要处理一些木棍，第一根的时间是1分钟，若后面一根木棍的长度和重量都大于等于前面一根的长度和重量，就不需要时间，否则需要1分钟，问如何安排处理木棍的顺序，才能使花的时间最少。

解题思路：贪心，把木棍先按照长度从小打到排序，若长度相同则按重量从小到大排序

#include <iostream>  #include <cstdio>  #include <cstring>  #include <string>  #include <algorithm>  #include <cmath>  #include <map>  #include <cmath>  #include <set>  #include <stack>  #include <queue>  #include <vector>  #include <bitset>  #include <functional>  using namespace std;#define LL long long  const int INF = 0x3f3f3f3f;int n,visit[5005];struct node{int l, w;}x[5005];bool cmp(node a, node b){if (a.l != b.l) return a.l < b.l;else return a.w < b.w;}int main(){int t;scanf("%d", &t);while (t--){scanf("%d", &n);for (int i = 1; i <= n; i++) scanf("%d%d", &x[i].l, &x[i].w);sort(x + 1, x + 1 + n,cmp);int sum = 0;memset(visit, 0, sizeof visit);for (int i = 1; i <= n; i++){if (visit[i]) continue;visit[i] = 1;int k = x[i].w;for (int j = i + 1; j <= n; j++)if (!visit[j] && k <= x[j].w)visit[j] = 1, k = x[j].w;sum++;}printf("%d\n", sum);}return 0;}