Java 列出所有组合
列出所有组合
实例源码：
源代码：
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//package com.nowjava;4
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import java.util.ArrayList;6
/**7
来 自 时 代 Java - nowjava.com8
**/9
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import java.util.Arrays;11
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import java.util.HashSet;13
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import java.util.List;15
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import java.util.Set;17
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public class Main {20
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public static void main(String[] argv) throws Exception {22
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int n = 2;24
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boolean zeroBased = true;26
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System.out.println(listAllCombinations(n, zeroBased));28
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}30
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public static List<Set<Integer>> listAllCombinations(int n,33
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boolean zeroBased) {35
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List<Set<Integer>> allCombinations;37
// 来自 时代Java - N o w J a v a . c o m38
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allCombinations = new ArrayList<Set<Integer>>();40
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for (int k = 0; k < n; k++) {42
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allCombinations.addAll(listCombinationsFixed2(n, k, zeroBased));44
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}46
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return allCombinations;49
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}51
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public static List<Set<Integer>> listCombinationsFixed2(final int n,54
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final int k, final boolean isZeroBased) {56
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List<Set<Integer>> combinations = new ArrayList<Set<Integer>>();58
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//System.out.println("will get combinations with (n,k)=(" + n + "," + k + ")");61
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Integer[] combination = null;64
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if (k == 0 || k == n) {67
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combination = new Integer[n];69
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for (int i = 0; i < n; i++) {71
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combination[i] = i;73
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}75
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} else {77
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combination = new Integer[k];79
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for (int i = 0; i < k; i++) {81
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combination[i] = i;83
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}85
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}87
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if (isZeroBased) {90
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combinations.add(new HashSet<Integer>(Arrays92
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.asList(combination)));94
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} else {96
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Integer[] tempCombination = new Integer[combination.length];98
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for (int i = 0; i < combination.length; i++) {101
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tempCombination[i] = combination[i] + 1;103
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}105
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combinations.add(new HashSet<Integer>(Arrays107
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.asList(tempCombination)));109
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}111
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while (nextCombination(combination, n, k)) {114
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if (isZeroBased) {117
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combinations.add(new HashSet<Integer>(Arrays119
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.asList(combination)));121
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} else {123
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Integer[] tempCombination = new Integer[combination.length];125
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for (int i = 0; i < combination.length; i++) {128
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tempCombination[i] = combination[i] + 1;130
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}132
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combinations.add(new HashSet<Integer>(Arrays134
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.asList(tempCombination)));136
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}138
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}141
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return combinations;144
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}146
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private static boolean nextCombination(Integer comb[], int n, int k) {149
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int i = k - 1;151
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if (i == -1) {153
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return false;155
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//System.out.println("NOT VALID INDEX, n:" + n + ", k:" + k);157
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}159
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++comb[i];162
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