HDU 1005 Wooden Sticks
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http://acm.hdu.edu.cn/showproblem.php?pid=1051
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).
(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
题解:贪心 先排序
时间复杂度:$O(N ^ 2 + N * logN)$
代码:
#include <bits/stdc++.h> using namespace std; const int maxn = 1e5 + 10; int N; struct Node { int l; int w; int flag; }node[maxn]; bool cmp(const Node& a, const Node& b) { return a.l == b.l ? a.w < b.w : a.l < b.l; } int main() { int T; scanf("%d", &T); while(T --) { memset(node, 0, sizeof(node)); scanf("%d", &N); for(int i = 1; i <= N; i ++) { scanf("%d%d", &node[i].l, &node[i].w); node[i].flag = 0; } int cnt = 0; sort(node + 1, node + 1 + N, cmp); for (int k = 1; k <= N;) { cnt ++; int L = 0, W = 0; for (int i = 1; i <= N; i ++) { if (!node[i].flag) if (node[i].l >= L && node[i].w >= W) { node[i].flag = 1; L = node[i].l; W = node[i].w; k ++; } } } printf("%d ", cnt); } return 0; }
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