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[5000];
        bool vis[5000] = { 0 };
        for (int i = 0; i < n; i++) {
            scanf("%d %d", &sticks[i].l, &sticks[i].w);
        }
        qsort(sticks, n, sizeof(sticks[0]), compare);
        int time = 0;
        for (int i = 0; i < n; i++) {
            if (vis[i])
                continue;
            int curw = sticks[i].w;
            for (int j = i + 1; j < n; j++) {
                if (!vis[j] && sticks[j].w >= curw) {
                    curw = sticks[j].w;
                    vis[j] = 1;
                }
            }
            time++;
        }
        printf("%d\n", time);
    }
　　　　return 0;
}