ACMSTEP 1.3.7 Wooden Sticks //排序 DP （LIS）

原题地址

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 562 Accepted Submission(s): 226

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

我记得这道题我以前在JOJ上做过，我还记得 是LIS （最长上升子序列的题） 有小半年的时间了。

但是看到这个题 感觉又不像是 LIS的题。仔细思索了一下，应该是在结构体按照长度排序完（我的代码中把weight写成了height。。），然后相同情况下同样从小到大排序重量，然后寻找有多少个递增子序列，有一个就需要那个1分钟。一次AC。

#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <cstdlib>#include <cctype>#include <string>#include <vector>#include <queue>#include <algorithm>using namespace std;struct sticks{int len;int height;}st[5005];int cmp1(const void*a, const void *b){if ((*(sticks *)a).len != (*(sticks *)b).len){return (*(sticks *)a).len - (*(sticks *)b).len;}else return (*(sticks *)a).height - (*(sticks *)b).height;}int main(){//freopen("c:\\in.txt","r",stdin);int cases, n, i, j;int used[5005];cin>>cases;while (cases--){cin>>n;for (i=0; i<n; i++){scanf ("%d %d",&st[i].len,&st[i].height);}qsort (st, n, sizeof(st[0]),cmp1);/*for (i=0; i<n; i++){cout<<st[i].len<<" "<<st[i].height<<endl;}*/int countn = 0, current;memset (used, 0, sizeof(used));for (i=0; i<n; i++){if (used[i]==0){current = st[i].height;used[i] = 1;countn++;for (j=1; j<n; j++){if (used[j]==0 && st[j].height >= current){current = st[j].height;used[j]=1;}}}}cout<<countn<<endl;}return 0;}