我正在做UVa Online Judge中著名的" the Blocks Problem"
我的方法很愚蠢,那是因为我想玩向量。我得到了指向堆中每个块的指针的向量,这些向量存储在一个叫做集合的向量中。
为了找到所有的块,我有一个叫做blockCollection的向量,其中存储了指向所有块的指针。
代码已通过提供的示例。我稍后会尝试编辑并提供注释。
全部来源:
#include <iostream>
#include <vector>
struct Block
{
int id;
std::vector<Block*>* where;
};
int positionInVector(Block* b);
int main(int argc, const char * argv[])
{
std::vector<std::vector<Block*>*> collection;
std::vector<Block*> blockCollection;
std::string command = "", command2 = "";
int blockCount = 0, k = 0, A = 0, B = 0;
while ( std::cin >> blockCount )
{
std::vector<Block*>* vectors = new std::vector<Block*>[blockCount];
Block* blocks = new Block[blockCount];
for ( k = 0 ; k < blockCount ; ++ k)
{
blocks[k].id = k;
blocks[k].where = &vectors[k];
vectors[k].push_back(&blocks[k]);
blockCollection.push_back(&blocks[k]);
collection.push_back(&vectors[k]);
}
std::cin >> std::ws;
while ( std::cin >> command )
{
if ( command == "quit" ) break;
std::cin >> A >> command2 >> B;
Block* blockA = blockCollection[A];
Block* blockB = blockCollection[B];
std::vector<Block*>* vectorA = blockA -> where;
std::vector<Block*>* vectorB = blockB -> where;
//exception handle
if ( A > blockCount || B > blockCount ) continue;
if ( A == B ) continue;
if ( vectorA == vectorB ) continue;
if ( command == "move" )
{
//move anything on top of A to its original position
int positionOfBlockAInVectorA = positionInVector(blockA);
for ( int i = positionOfBlockAInVectorA + 1 ; i < vectorA -> size() ; ++ i )
{
Block* blockToBeMoved = *(vectorA -> begin() + i);
std::vector<Block*>* destinationVector = collection[blockToBeMoved -> id];
blockToBeMoved -> where = destinationVector;
destinationVector -> push_back(blockToBeMoved);
}
vectorA -> erase(vectorA -> begin() + positionOfBlockAInVectorA + 1, vectorA -> end());
}
if ( command2 == "onto" )
{
//move anything on top of B to its original position
int positionOfBlockBInVectorB = positionInVector(blockB);
for ( int i = positionOfBlockBInVectorB + 1 ; i < vectorB -> size() ; ++ i )
{
Block* blockToBeMoved = *(vectorB -> begin() + i);
std::vector<Block*>* destinationVector = collection[blockToBeMoved -> id];
blockToBeMoved -> where = destinationVector;
destinationVector -> push_back(blockToBeMoved);
}
if (positionOfBlockBInVectorB + 1 > vectorB -> size()) vectorA -> erase(vectorB -> begin() + positionOfBlockBInVectorB + 1, vectorB -> end());
}
if ( command == "move" )
{
//move block a to the pile containing block b
vectorA -> pop_back();
blockA -> where = vectorB;
vectorB -> push_back(blockA);
}
else
{
//move block a and those on top of it to the pile containing block b
std::vector<Block*> temperaryVector;
int positionOfBlockAInVectorA = positionInVector(blockA);
for ( int i = (int)vectorA -> size() - 1 ; i >= positionOfBlockAInVectorA ; -- i )
{
temperaryVector.push_back(vectorA -> at(i));
vectorA -> erase(vectorA -> begin() + i);
}
for ( int i = (int)temperaryVector.size() - 1 ; i >= 0 ; -- i )
{
temperaryVector[i] -> where = vectorB;
vectorB -> push_back(temperaryVector[i]);
}
}
}
for ( k = 0 ; k < blockCount ; ++ k )
{
std::vector<Block*>* vector = collection[k];
std::cout << k << ":";
if ( !vector -> empty() )
{
for ( int i = 0 ; i < vector -> size() ; ++ i )
{
std::cout << " " << vector -> at(i) -> id;
}
}
std::cout << std::endl;
}
delete [] blocks;
delete [] vectors;
}
return 0;
}
int positionInVector(Block* block)
{
std::vector<Block*> vector = *block -> where;
for ( int i = 0 ; i < vector.size() ; ++ i )
{
if ( vector[i] == block ) return i;
}
return -1;
}
谢谢!
要让它起作用:
A = (int)command[5] - 48;
B = (int)command[12] - 48;
我们需要确保字符串长度为5/12个字符,并且在这些位置上有一个数字。代码应该检查输入的长度和这些地方的数字的有效性。
每当你在blockCollection中添加或删除一个Block时,你持有的指向集合中任何Block的指针都可能无效。
我想这就是我最初需要说的…