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//Bipartite graphic and maximum matching with Hungarian algorithm.
/
#include <list>
#include <cstring>using namespace std;const int MAX_LEFT = 500;
const int MAX_RIGHT = 500;class Bipartite {
private:struct Edge {int to;Edge* next;Edge(int _to) {to = _to;}};Edge* m_adjList[MAX_LEFT];int m_lCnt;int m_rCnt;int m_lMatchR[MAX_RIGHT];int m_rMatchL[MAX_LEFT];int m_preL[MAX_LEFT];bool m_visitR[MAX_RIGHT];//This matrix is just used to prevent adding two repeated edges.bool m_matrix[MAX_LEFT][MAX_RIGHT];void clear() {for (int i = 0; i < m_lCnt; i++) {Edge* e = m_adjList[i];while (e != NULL) {Edge* pre = e;e = e->next;delete pre;}m_adjList[i] = NULL;}memset(m_matrix, 0, sizeof(m_matrix));}void findAugment(int start) {for (int i = 0; i < m_lCnt; i++) {m_preL[i] = -1;}memset(m_visitR, 0, sizeof(bool) * m_rCnt);list<int> que;que.push_back(start);bool found = false;while (!que.empty() && !found) {int from = que.front();que.pop_front();Edge* edge = m_adjList[from];while (edge != NULL && !found) {int to = edge->to;if (!m_visitR[to]) {m_visitR[to] = true;if (m_rMatchL[to] == -1) {found = true;reverse(from, to);}else {que.push_back(m_rMatchL[to]);m_preL[m_rMatchL[to]] = from;}}edge = edge->next;}}}void reverse(int left, int right) {m_rMatchL[right] = left;while(m_preL[left] != -1) {int nextR = m_lMatchR[left];m_rMatchL[nextR] = m_preL[left];m_lMatchR[left] = right;left = m_preL[left];right = nextR;}m_lMatchR[left] = right;}public:Bipartite() {memset(m_adjList, 0, sizeof(m_adjList));m_lCnt = 0;m_rCnt = 0;}~Bipartite() {clear();}//Add an edge between vertex "left" and "right" while "left" and "right" are//the indices of two vertices in the left/right parts of the graph. Indices//in the left and right parts are separated and they both begin from 0.void addEdge(int left, int right) {if (!m_matrix[left][right]) {m_matrix[left][right] = true;Edge* newEdge = new Edge(right);newEdge->next = m_adjList[left];m_adjList[left] = newEdge;}}//Before invoking this function, "maxMatch()" must be invoked. This function//returns the index of the matching vertex of "left" while "left" is the//index of a vertex in the left part of the graphic.int getLMatchR(int left) const {return m_lMatchR[left];}//See "getLMatchR()", and this function is opposite to it.int getRMatchL(int right) const {return m_rMatchL[right];}void init(int leftCnt, int rightCnt) {clear();m_lCnt = leftCnt;m_rCnt = rightCnt;for (int i = 0; i < m_lCnt; i++) {m_lMatchR[i] = -1;}for (int i = 0; i < m_rCnt; i++) {m_rMatchL[i] = -1;}}int maxMatch() {for (int i = 0; i < m_lCnt; i++) {findAugment(i);}int result = 0;for (int i = 0; i < m_lCnt; i++) {if (m_lMatchR[i] != -1) {result++;}}return result;}
};//Test suites.
#include <iostream>int main() {Bipartite match;match.init(300, 400);int a[] = {0, 0, 1, 1, 2, 2, 2};int b[] = {1, 2, 1, 3, 0, 1, 2};for (int i = 0; i < 7; i++) {match.addEdge(a[i], b[i]);}int maxMatch = match.maxMatch();cout << maxMatch << " ";for (int i = 0; i < 3; i++) {cout << match.getLMatchR(i) << " ";}for (int i = 0; i < 4; i++) {cout << match.getRMatchL(i) << " ";}cout << endl;//Correct: 3 2 3 1 -1 2 0 1return 0;
}