109 lines
2.1 KiB
C++
109 lines
2.1 KiB
C++
/*
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2003-2006 Erwin Coumans http://continuousphysics.com/Bullet/
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This software is provided 'as-is', without any express or implied warranty.
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In no event will the authors be held liable for any damages arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it freely,
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subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#include "UnionFind.h"
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#include <assert.h>
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int UnionFind::find(int x)
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{
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assert(x < m_N);
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assert(x >= 0);
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while (x != m_id[x])
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{
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//not really a reason not to use path compression, and it flattens the trees/improves find performance dramatically
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#define USE_PATH_COMPRESSION 1
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#ifdef USE_PATH_COMPRESSION
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//
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m_id[x] = m_id[m_id[x]];
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#endif //
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x = m_id[x];
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assert(x < m_N);
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assert(x >= 0);
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}
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return x;
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}
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UnionFind::~UnionFind()
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{
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Free();
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}
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UnionFind::UnionFind()
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:m_id(0),
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m_sz(0),
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m_N(0)
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{
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}
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void UnionFind::Allocate(int N)
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{
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if (m_N < N)
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{
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Free();
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m_N = N;
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m_id = new int[N];
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m_sz = new int[N];
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}
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}
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void UnionFind::Free()
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{
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if (m_N)
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{
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m_N=0;
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delete m_id;
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delete m_sz;
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}
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}
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void UnionFind::reset(int N)
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{
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Allocate(N);
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for (int i = 0; i < m_N; i++)
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{
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m_id[i] = i; m_sz[i] = 1;
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}
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}
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int UnionFind ::find(int p, int q)
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{
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return (find(p) == find(q));
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}
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void UnionFind ::unite(int p, int q)
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{
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int i = find(p), j = find(q);
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if (i == j)
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return;
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//weighted quick union, this keeps the 'trees' balanced, and keeps performance of unite O( log(n) )
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if (m_sz[i] < m_sz[j])
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{
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m_id[i] = j; m_sz[j] += m_sz[i];
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}
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else
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{
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m_id[j] = i; m_sz[i] += m_sz[j];
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}
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}
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