HDOJ-1051 Wooden sticks（贪心）

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 19672    Accepted Submission(s): 7991

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

2
1
3

 

题目大意：有个木材加工机器，第一个放入的木材要花1分钟加工，若接下来放入的木材的长度和重量都大于等于前一个放入的木材，则这个木材加工花费的时间为零，否则得花费一分钟时间来加工；以此类推，直到木材加工完为止。

思想：结构体二级排序，对其中一个属性贪心。

 

 

代码：

 #include <stdio.h>
 #include <stdbool.h>
 #include <stdlib.h>
 typedef struct wood {
     int l;
     int w;
 }Wood;
 int compare(const void * p1, const void * p2) {
     Wood * a1 = (Wood *)p1;
     Wood * a2 = (Wood *)p2;
     if (a1->l != a2->l)
         return a1->l - a2->l;
     else
         return a1->w - a2->w;
 }
 int main(void)
 {
     int T;
     scanf("%d", &T);
     while (T--) {
         int n;
         scanf("%d", &n);
         Wood sticks[];
         bool vis[] = {  };
         for (int i = ; i < n; i++) {
             scanf("%d %d", &sticks[i].l, &sticks[i].w);
         }
         qsort(sticks, n, sizeof(sticks[]), compare);
         int time = ;
         for (int i = ; i < n; i++) {
             if (vis[i])
                 continue;
             int curw = sticks[i].w;
             for (int j = i + ; j < n; j++) {
                 if (!vis[j] && sticks[j].w >= curw) {
                     curw = sticks[j].w;
                     vis[j] = ;
                 }
             }
             time++;
         }
         printf("%d\n", time);
     }
　　　　return 0;
 }