【HDU】1051 - Wooden Sticks（贪心 & 二分 || 动态规划）

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Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 18101    Accepted Submission(s): 7387

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

 

Source

Asia 2001, Taejon (South Korea)

 

和上一道题差不多，不过这次是升序，g 数组里的数肯定是降序排列的，用lower_bound ( )就不会用了，手写了二分也能过。

这样是用贪心的方法做的。最下面贴出 LIS 的做法。

代码如下：

#include <cstdio>#include <algorithm>#define INF 0x3f3f3f3fusing namespace std;int ans;struct wood{int l,w;}data[5000+11];bool cmp(wood a , wood b){if (a.l == b.l)return a.w < b.w;return a.l < b.l;}int g[5000+11];int find(int x){int l = 1;int r = ans;int mid;while (r >= l){mid = (l + r) >> 1;if (g[mid] > x)//二分的判断条件还是有点晕 l = mid + 1;elser = mid - 1;}return l;}int main(){int u;int n;scanf ("%d",&u);while (u--){scanf ("%d",&n);for (int i = 1 ; i <= n ; i++){scanf ("%d %d",&data[i].l,&data[i].w);g[i] = INF;}sort (data + 1 , data + 1 + n , cmp);ans = 0;int pos;for (int i = 1 ; i <= n ; i++){pos = find(data[i].w);g[pos] = data[i].w;ans = max (ans , pos);}printf ("%d\n",ans);}return 0;}