维特比算法，红白球

import java.text.DecimalFormat;public class ViterbiBall {//观察集合private enum V{RED,WHITE}//状态private enum Q{BOX1,BOX2,BOX3}private static int QLength = Q.values().length;//转移概率private static float[][] A = new float[][]{{0.5f,0.2f,0.3f},{0.3f,0.5f,0.2f},{0.2f,0.3f,0.5f}};//观察概率private static float[][] B = new float[][]{{0.5f,0.5f},{0.4f,0.6f},{0.7f,0.3f}};//初始概率private static float[] PI = new float[]{0.2f,0.4f,0.4f};//观察序列private static V[] O = new V[]{V.RED,V.WHITE,V.RED}; //初始化private static float[] init = new float[QLength];/** * 初始化数据 */private void initData(){for(int i=0;i<QLength;i++){init[i] = PI[i]*B[i][O[0].ordinal()];}}/** * 维特比算法 * @param i * @return */private ViterbiData[] viterbi(int i){if(i==2){ViterbiData[] ViterbiDataTemp = new ViterbiData[QLength];for(int k=0;k<QLength;k++){float max=0;int[] maxIndex= new int[O.length];for(int j=0;j<QLength;j++){float t = init[k]*A[j][k]*B[k][O[i-1].ordinal()];if(t>=max){max = t;maxIndex[0] = k;}}ViterbiDataTemp[k]=new ViterbiData(maxIndex, max);}return ViterbiDataTemp;}ViterbiData[] previousData = viterbi(i-1);ViterbiData[] ViterbiDataTemp = new ViterbiData[QLength];for(int k=0;k<QLength;k++){float max=0;int[] maxIndex = previousData[k].getStatePath();for(int j=0;j<QLength;j++){float t = previousData[k].getMaxProbility()*A[j][k]*B[k][O[i-1].ordinal()];if(t>=max){max = t;maxIndex[i-2] = k;}}ViterbiDataTemp[k]=new ViterbiData(maxIndex, max);}if(i==O.length){float finalMax = 0;int finalIndex = 0;for(int k=0;k<QLength;k++){float temp = ViterbiDataTemp[k].getMaxProbility();if(temp>=finalMax){finalMax = temp;finalIndex = k;}}int[] statePath =  ViterbiDataTemp[finalIndex].getStatePath();statePath[i-1] = finalIndex;System.out.println("状态序列：");for(int j = statePath.length-1;j>=0; j--){System.out.print(Q.values()[statePath[j]]+" ");}System.out.println("\n最大概率：");DecimalFormat df = new DecimalFormat( "#.#####");   System.out.println(df.format(finalMax));return null;}return ViterbiDataTemp;}public static void main(String[] args) {ViterbiBall v = new ViterbiBall();v.initData();v.viterbi(O.length);}}/** * 存放递归时候传递数据的类，statePath是状态序列。maxProbility是每次最大的概率值。 * @author ailab * */class ViterbiData{private int statePath[];private float maxProbility;public int[] getStatePath() {return statePath;}public void setStatePath(int[] statePath) {this.statePath = statePath;}public float getMaxProbility() {return maxProbility;}public void setMaxProbility(float maxProbility) {this.maxProbility = maxProbility;}public ViterbiData(int[] statePath,float maxProbility){this.statePath = statePath;this.maxProbility = maxProbility;}}