HDU 1051：Wooden Sticks【贪心】

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 16237    Accepted Submission(s): 6665

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

 

AC-code:

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;struct node{int x,y;}s[5005];bool cmp(node a,node b){if(a.x==b.x)return a.y<b.y;return a.x<b.x;}int c[5005];int main(){int T,n,i,j,cnt,flag;scanf("%d",&T);while(T--){scanf("%d",&n);for(i=0;i<n;i++)scanf("%d%d",&s[i].x,&s[i].y);sort(s,s+n,cmp);cnt=0;memset(c,0,sizeof(c));for(i=0;i<n;i++)if(!c[i]){flag=s[i].y;for(j=i+1;j<n;j++)if(!c[j]&&s[j].y>=flag)flag=s[j].y,c[j]=1;c[i]=1;cnt++;}printf("%d\n",cnt); }  return 0;}