Edmonds-Karp算法

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最大流算法

参考：http://www.cnblogs.com/jackge/archive/2013/05/05/3061893.html

package test;import java.util.Arrays;import java.util.LinkedList;public class Edmonds_Karp_Test {public static void main(String[] args) {//输入一个图int [][] cap ={  {0,5,0,0,0},  {0,0,6,0,1},        {0,0,0,5,2},        {0,0,0,0,1},        {0,0,0,0,0},        };//有向图的初始容量int max=EdmondsKarp(0, 4, cap);System.out.println(max);}public static int EdmondsKarp(int start,int end,int[][] cap){int [][] flow =new int [cap.length][cap[0].length];//记录流量int [] pre = new int[cap.length];//记录前一个节点int [] rest = new int[cap.length];//记录剩余的流量，残量int maxflow = 0;for(int i=0;i<flow.length;i++){Arrays.fill(flow[i], 0);}Arrays.fill(pre, 0);LinkedList list = new LinkedList<Integer>();while(true){//System.out.println("yici");for(int j =0 ;j<rest.length;j++){//设置残量都为0rest[j] =0;}rest[start] = 10000000;//设置起始位置的残量为一个很大的值list.add(start);while(!list.isEmpty()){//BFS 寻找增广路//System.out.println("yici");int u = (int)list.pollFirst();for(int v =0;v<=end;v++){if(rest[v]==0 && cap[u][v]-flow[u][v] > 0){pre[v] =u;//设置前面的节点rest[v] = Math.min(rest[u], cap[u][v]-flow[u][v]);//获取start到v节点的最小残量list.add(v);}}}//System.out.println(rest[end]+"rest[end]");maxflow += rest[end];if(rest[end] == 0){return maxflow;}for(int u=end;u!=start;u=pre[u]){//从汇点往回走flow[pre[u]][u] += rest[end];//更新正向流flow[u][pre[u]] -= rest[end];//更新反向流System.out.print(u+" ");}System.out.print(start+"  ");System.out.println("寻找至本次的流为： "+maxflow);}//return maxflow;}//}

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