最大二分匹配
二分匹配是指图中的一组边以这样的方式选择,以致于集合中的任何两条边都不会共享一个端点。最大匹配是匹配的最大边数。
找到最大匹配后,我们不能再添加任何边。如果将一条边添加到最大匹配图中,它将不再是匹配。对于二分图,可以存在多个最大匹配。
输入和输出
Input: The adjacency matrix. 0 1 1 0 0 0 1 0 0 1 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 Output: Maximum number of applicants matching for job: 5
算法
bipartiteMatch(u, visited, assign)
输入: 起始节点、已访问列表用于追踪、分配列表将节点分配给另一个节点。
输出 − 当可能为顶点 u 匹配时返回 true。
Begin for all vertex v, which are adjacent with u, do if v is not visited, then mark v as visited if v is not assigned, or bipartiteMatch(assign[v], visited, assign) is true, then assign[v] := u return true done return false End
maxMatch(图)
输入 − 给定的图。
输出 − 匹配的最大数量。
Begin initially no vertex is assigned count := 0 for all applicant u in M, do make all node as unvisited if bipartiteMatch(u, visited, assign), then increase count by 1 done End
示例
#include <iostream> #define M 6 #define N 6 using namespace std; bool bipartiteGraph[M][N] = { //A graph with M applicant and N jobs {0, 1, 1, 0, 0, 0}, {1, 0, 0, 1, 0, 0}, {0, 0, 1, 0, 0, 0}, {0, 0, 1, 1, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 1} }; bool bipartiteMatch(int u, bool visited[], int assign[]) { for (int v = 0; v < N; v++) { //for all jobs 0 to N-1 if (bipartiteGraph[u][v] && !visited[v]) { //when job v is not visited and u is interested visited[v] = true; //mark as job v is visited //when v is not assigned or previously assigned if (assign[v] < 0 || bipartiteMatch(assign[v], visited, assign)) { assign[v] = u; //assign job v to applicant u return true; } } } return false; } int maxMatch() { int assign[N]; //an array to track which job is assigned to which applicant for(int i = 0; i<N; i++) assign[i] = -1; //initially set all jobs are available int jobCount = 0; for (int u = 0; u < M; u++) { //for all applicants bool visited[N]; for(int i = 0; i<N; i++) visited[i] = false; //initially no jobs are visited if (bipartiteMatch(u, visited, assign)) //when u get a job jobCount++; } return jobCount; } int main() { cout << "Maximum number of applicants matching for job: " << maxMatch(); }
输出
Maximum number of applicants matching for job: 5
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