UVA - 101 The Blocks Problem
2015-10-05 10:42
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Description
![](http://uva.onlinejudge.org/components/com_onlinejudge/images/button_pdf.png)
In this problem you will model a simple block world under certain rules and constraints. Rather than determine how to achieve a specified state, you will ``program'' a robotic arm to respond to a limited set of commands.
n blocks on the table (numbered from 0 to n-1) with block bi adjacent to block
bi+1 for all
![](http://7xjob4.com1.z0.glb.clouddn.com/410b9d94c796bc3fef344e9c5322e236)
as shown in the diagram below:
Figure: Initial Blocks World
The valid commands for the robot arm that manipulates blocks are:
move a onto b
where a and b are block numbers, puts block a onto block
b after returning any blocks that are stacked on top of blocks a and
b to their initial positions.
move a over b
where a and b are block numbers, puts block a onto the top of the stack containing block
b, after returning any blocks that are stacked on top of block a to their initial positions.
pile a onto b
where a and b are block numbers, moves the pile of blocks consisting of block
a, and any blocks that are stacked above block a, onto block
b. All blocks on top of block b are moved to their initial positions prior to the pile taking place. The blocks stacked above block
a retain their order when moved.
pile a over b
where a and b are block numbers, puts the pile of blocks consisting of block
a, and any blocks that are stacked above block a, onto the top of the stack containing block
b. The blocks stacked above block a retain their original order when moved.
quit
terminates manipulations in the block world.
Any command in which a = b or in which a and b are in the same stack of blocks is an illegal command. All illegal commands should be ignored and should have no affect on the configuration of blocks.
n < 25.
The number of blocks is followed by a sequence of block commands, one command per line. Your program should process all commands until the
quit command is encountered.
You may assume that all commands will be of the form specified above. There will be no syntactically incorrect commands.
i (
![](http://7xjob4.com1.z0.glb.clouddn.com/c3a02bffb423974a9d18bb78ff246bdf)
where
n is the number of blocks) should appear followed immediately by a colon. If there is at least a block on it, the colon must be followed by one space, followed by a list of blocks that appear stacked in that position with each block number separated
from other block numbers by a space. Don't put any trailing spaces on a line.
There should be one line of output for each block position (i.e., n lines of output where
n is the integer on the first line of input).
分析:算法竞赛这类题很适合用c++写,用vector,很方便;要注意的是对‘move’和‘onto’的处理,还有指令有效性判断
![](http://uva.onlinejudge.org/components/com_onlinejudge/images/button_pdf.png)
Background
Many areas of Computer Science use simple, abstract domains for both analytical and empirical studies. For example, an early AI study of planning and robotics (STRIPS) used a block world in which a robot arm performed tasks involving the manipulation of blocks.In this problem you will model a simple block world under certain rules and constraints. Rather than determine how to achieve a specified state, you will ``program'' a robotic arm to respond to a limited set of commands.
The Problem
The problem is to parse a series of commands that instruct a robot arm in how to manipulate blocks that lie on a flat table. Initially there aren blocks on the table (numbered from 0 to n-1) with block bi adjacent to block
bi+1 for all
as shown in the diagram below:
The valid commands for the robot arm that manipulates blocks are:
move a onto b
where a and b are block numbers, puts block a onto block
b after returning any blocks that are stacked on top of blocks a and
b to their initial positions.
move a over b
where a and b are block numbers, puts block a onto the top of the stack containing block
b, after returning any blocks that are stacked on top of block a to their initial positions.
pile a onto b
where a and b are block numbers, moves the pile of blocks consisting of block
a, and any blocks that are stacked above block a, onto block
b. All blocks on top of block b are moved to their initial positions prior to the pile taking place. The blocks stacked above block
a retain their order when moved.
pile a over b
where a and b are block numbers, puts the pile of blocks consisting of block
a, and any blocks that are stacked above block a, onto the top of the stack containing block
b. The blocks stacked above block a retain their original order when moved.
quit
terminates manipulations in the block world.
Any command in which a = b or in which a and b are in the same stack of blocks is an illegal command. All illegal commands should be ignored and should have no affect on the configuration of blocks.
The Input
The input begins with an integer n on a line by itself representing the number of blocks in the block world. You may assume that 0 <n < 25.
The number of blocks is followed by a sequence of block commands, one command per line. Your program should process all commands until the
quit command is encountered.
You may assume that all commands will be of the form specified above. There will be no syntactically incorrect commands.
The Output
The output should consist of the final state of the blocks world. Each original block position numberedi (
where
n is the number of blocks) should appear followed immediately by a colon. If there is at least a block on it, the colon must be followed by one space, followed by a list of blocks that appear stacked in that position with each block number separated
from other block numbers by a space. Don't put any trailing spaces on a line.
There should be one line of output for each block position (i.e., n lines of output where
n is the integer on the first line of input).
Sample Input
10 move 9 onto 1 move 8 over 1 move 7 over 1 move 6 over 1 pile 8 over 6 pile 8 over 5 move 2 over 1 move 4 over 9 quit
Sample Output
0: 0 1: 1 9 2 4 2: 3: 3 4: 5: 5 8 7 6 6: 7: 8: 9:
分析:算法竞赛这类题很适合用c++写,用vector,很方便;要注意的是对‘move’和‘onto’的处理,还有指令有效性判断
#include <iostream> #include <vector> #include <string> #include <cstdio> using namespace std; const int maxn = 30; vector<int> pile[maxn]; int n; //找木块a所在的pile和height void find_block(int a, int& p, int& h) { for(p=0; p<n; p++) for(h=0; h<pile[p].size(); h++) if(pile[p][h]==a)return; } //把第p堆高度为h的木块上方的所有木块移回原位 void clear_above(int p, int h) { for(int i=h+1; i<pile[p].size(); i++) { int b = pile[p][i]; pile[b].push_back(b); } pile[p].resize(h+1); } //把第p堆高度为h及其上方的木块整体移到p2堆的顶部 void pile_onto(int p, int h, int p2) { for(int i=h; i<pile[p].size(); i++) { pile[p2].push_back(pile[p][i]); } pile[p].resize(h); } void print() { for(int i=0; i<n; i++) { printf("%d:",i); for(int j=0; j<pile[i].size(); j++) printf(" %d",pile[i][j]); putchar('\n'); } } int main() { int a,b; cin >> n; string s1,s2; for(int i=0; i<n; i++) pile[i].push_back(i); while(cin>>s1>>a>>s2>>b) { int pa,pb,ha,hb; find_block(a,pa,ha); find_block(b,pb,hb); if(pa==pb)continue; if(s1=="move")clear_above(pa,ha); if(s2=="onto")clear_above(pb,hb); pile_onto(pa,ha,pb); } print(); return 0; }
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