hdu 1051 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
--------------------------------------------------------------------------------------------
这也是一个重要的知识点，求一个序列中 增序列，或者降序列的个数；
这道题：是求降序列的个数，或者说是升序列的个数（这个序列，是特殊的序列）
这道题，和最少导弹拦截系统，是类似的，原理是一样的；
先按升序排序
用一个数组d先记录第一个元素的w，然后，对于后面的元素，到这个数组里找，如果，后面的元素的w大于等于这个数组d中的任何一个元素(x)，同时要更新数组d中的这个元素x(只要有一个就跳出)，否则，将这个元素加到这个数组d中;这样后面的每一个元素都要到数组d中查找，就可以了；
#include<stdio.h>#include<stdlib.h>#include<string.h>struct wood{int l,w;}a[5050];int cmp(const void *a ,const void *b){struct wood *c = (struct wood*)a;struct wood *d = (struct wood*)b;if(c->l==d->l)return c->w - d->w;elsereturn c->l - d->l;}int main(){int t,n,count;int d[1000];int i,j;scanf("%d",&t);while(t--){scanf("%d",&n);memset(a,0,sizeof(a));memset(d,0,sizeof(d));for(i=0;i<n;i++)scanf("%d%d",&a[i].l,&a[i].w);qsort(a,n,sizeof(a[0]),cmp);//sort(a,a+n,cmp);count=1;d[0] = a[0].w;for(i=1;i<n;i++){for(j=0;j<count;j++){if(a[i].w>=d[j]){d[j] = a[i].w;break;}}if(j==count){//if(a[i].w<d[j-1]) // 因为上面已经 考虑到a[i].w = d[j]的情况，所以这里只有小于的情况，不用再判断；//{d[j] = a[i].w;count++;//}}}printf("%d\n",count);}return 0;}