HDU 1950 Bridging signals
Bridging signals
Time Limit: 5000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 3402 Accepted Submission(s):
2141
Problem Description
'Oh no, they've done it again', cries the chief
designer at the Waferland chip factory. Once more the routing designers have
screwed up completely, making the signals on the chip connecting the ports of
two functional blocks cross each other all over the place. At this late stage of
the process, it is too
expensive to redo the routing. Instead, the engineers have to bridge the signals, using the third dimension, so that no two signals cross. However, bridging is a complicated operation, and thus it is desirable to bridge as few signals as possible. The call for a computer program that finds the maximum number of signals which may be connected on the silicon surface without rossing each other, is imminent. Bearing in mind that there may be housands of signal ports at the boundary of a functional block, the problem asks quite a lot of the programmer. Are you up to the task?
Figure 1. To the left: The two blocks' ports and their signal mapping (4,2,6,3,1,5). To the right: At most three signals may be routed on the silicon surface without crossing each other. The dashed signals must be bridged.
A typical situation is schematically depicted in figure 1. The ports of the two functional blocks are numbered from 1 to p, from top to bottom. The signal mapping is described by a permutation of the numbers 1 to p in the form of a list of p unique numbers in the range 1 to p, in which the i:th number pecifies which port on the right side should be connected to the i:th port on the left side.
Two signals cross if and only if the straight lines connecting the two ports of each pair do.
expensive to redo the routing. Instead, the engineers have to bridge the signals, using the third dimension, so that no two signals cross. However, bridging is a complicated operation, and thus it is desirable to bridge as few signals as possible. The call for a computer program that finds the maximum number of signals which may be connected on the silicon surface without rossing each other, is imminent. Bearing in mind that there may be housands of signal ports at the boundary of a functional block, the problem asks quite a lot of the programmer. Are you up to the task?
Figure 1. To the left: The two blocks' ports and their signal mapping (4,2,6,3,1,5). To the right: At most three signals may be routed on the silicon surface without crossing each other. The dashed signals must be bridged.
A typical situation is schematically depicted in figure 1. The ports of the two functional blocks are numbered from 1 to p, from top to bottom. The signal mapping is described by a permutation of the numbers 1 to p in the form of a list of p unique numbers in the range 1 to p, in which the i:th number pecifies which port on the right side should be connected to the i:th port on the left side.
Two signals cross if and only if the straight lines connecting the two ports of each pair do.
Input
On the first line of the input, there is a single
positive integer n, telling the number of test scenarios to follow. Each test
scenario begins with a line containing a single positive integer p<40000, the
number of ports on the two functional blocks. Then follow p lines, describing
the signal mapping: On the i:th line is the port number of the block on the
right side which should be connected to the i:th port of the block on the left
side.
Output
For each test scenario, output one line containing the
maximum number of signals which may be routed on the silicon surface without
crossing each other.
Sample Input
4
6
4
2
6
3
1
5
10
2
3
4
5
6
7
8
9
10
1
8
8
7
6
5
4
3
2
1
9
5
8
9
2
3
1
7
4
6
Sample Output
3
9
1
4
题目大意：两点之间有一条线，问不想交的线最多有几条。
#include<iostream> #include <cstdio> #include <string> #include <algorithm> #include <cstring> using namespace std; #define MAXN 40002 int a[MAXN], d[MAXN]; int main() { int T; scanf("%d",&T);//cin会超时 while (T--) { int n; cin >> n; for (int i = 1; i <= n; i++) scanf("%d", &a[i]); int len = 1; d[1] = a[1]; int i; for (i = 2; i <= n; i++) { if (a[i] > d[len]) { d[++len] = a[i]; continue; } int j;//二分 int le = 1, ri = len; while (le <= ri) { j = (le + ri) / 2; if (a[i]>=d[j]) { le = j + 1; } else ri = j - 1; } d[le] = a[i];//不能是d[ri] = a[i];，因为替换的是比它略大的数，此时le>ri } printf("%d\n", len); } return 0; }
