Java 實現常見排序算法

1. 綜述

　　復習常見排序算法，用Java實現。

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2. 代碼

1 package cn.edu.tju.scs; 2 3 public class Sort { 4 public static void main(String [] args){ 5 6 int[] intArray = {3, 5, 1, 4, 7, 9, 8, 2, 6}; 7 System.out.print("排序前：");print(intArray); 8 long beginTime = System.nanoTime(); 9 10 // bubbleSort(intArray); 11 // selectSort(intArray); 12 // insertionSort(intArray); 13 // mergeSort(intArray); 14 // quickSort(intArray); 15 // heapSort(intArray); 16 17 long endTime = System.nanoTime(); 18 System.out.print("排序后：");print(intArray); 19 System.out.println("用時：" + (endTime - beginTime) + "ns"); 20 } 21 22 private static void heapSort(int[] intArray) { 23 // build Max Heap 24 for (int i = intArray.length - 1; i >= 0; i--) 25 maxHeapify(intArray, intArray.length - 1, i); 26 27 for (int i = intArray.length - 1; i > 0; i--) { 28 swap(intArray, 0, i); 29 maxHeapify(intArray, i - 1, 0); 30 } 31 } 32 33 private static void maxHeapify(int[] intArray, int lastNode, int rootNode) { 34 int lchild = 2 * rootNode + 1; 35 int rchild = lchild + 1; 36 37 // has two children 38 while (lchild < lastNode) { 39 if (intArray[rootNode] >= intArray[lchild] && intArray[rootNode] >= intArray[rchild]) 40 return; 41 42 if (intArray[lchild] >= intArray[rchild]) { 43 swap(intArray, lchild, rootNode); 44 rootNode = lchild; 45 } else { 46 swap(intArray, rchild, rootNode); 47 rootNode = rchild; 48 } 49 lchild = 2 * rootNode + 1; 50 rchild = lchild + 1; 51 } 52 // has only left child 53 if (lchild == lastNode) { 54 if (intArray[rootNode] < intArray[lchild]) 55 swap(intArray, lchild, rootNode); 56 } 57 } 58 59 private static void quickSort(int[] intArray) { 60 quickSort(intArray, 0, intArray.length - 1); 61 } 62 63 private static void quickSort(int[] intArray, int begin, int end) { 64 if (end - begin < 1) return; 65 if (end - begin < 2){ 66 if (intArray[end] < intArray[begin]) 67 swap(intArray, begin, end); 68 return; 69 } 70 // partition begin 71 int left = begin; 72 int right = end; 73 int x = intArray[left]; 74 while (left < right) { 75 while (intArray[right] >= x && left < right) 76 right--; 77 if (left < right){ 78 intArray[left] = intArray[right]; 79 left++; 80 } 81 82 while (intArray[left] < x && left < right) 83 left++; 84 if (left < right){ 85 intArray[right] = intArray[left]; 86 right--; 87 } 88 } 89 intArray[right] = x; 90 // partition end 91 quickSort(intArray, begin, right - 1); 92 quickSort(intArray, right + 1, end); 93 } 94 95 private static void mergeSort(int[] intArray) { 96 mergeSort(intArray, 0, intArray.length - 1); 97 } 98 99 private static void mergeSort(int[] intArray, int begin, int end) { 100 if (end - begin < 2){ 101 // sort 2 number 102 if (intArray[begin] > intArray[end]) 103 swap(intArray, begin, end); 104 } else { 105 int mid = (begin + end) / 2; 106 mergeSort(intArray, begin, mid); 107 mergeSort(intArray, mid + 1, end); 108 merge(intArray, begin, mid, end); 109 } 110 } 111 112 private static void merge(int[] intArray, int begin, int mid, int end) { 113 int [] tmpArray = new int[end - begin + 1]; 114 int iter1 = begin; 115 int iter2 = mid + 1; 116 int i = 0; 117 while (iter1 <= mid && iter2 <= end) { 118 if (intArray[iter2] < intArray[iter1]) { 119 tmpArray[i] = intArray[iter2]; 120 iter2++; 121 i++; 122 } else { 123 tmpArray[i] = intArray[iter1]; 124 iter1 ++; 125 i++; 126 } 127 } 128 if (iter1 > mid){ 129 for (int j = iter2; j <= end; j++) { 130 tmpArray[i++] = intArray[j]; 131 } 132 } 133 if (iter2 > end){ 134 for (int j = iter1; j <= mid; j++){ 135 tmpArray[i++] = intArray[j]; 136 } 137 } 138 for (i = 0; i < tmpArray.length; i++) 139 intArray[begin + i] = tmpArray[i]; 140 } 141 142 private static void insertionSort(int[] intArray) { 143 144 for (int i = 1; i < intArray.length; i++) { 145 int flag = i; 146 if (intArray[flag] >= intArray[flag - 1]) 147 continue; 148 int temp = intArray[flag]; // temp need to inserted into the sequence 149 if (intArray[flag] < intArray[0]) { 150 // move all items one back 151 for (int j = flag; j > 0; j--) { 152 intArray[j] = intArray[j - 1]; 153 } 154 intArray[0] = temp; 155 } else { // need insertion 156 int left = 0, right = flag - 1, mid = 0; 157 while (right - left != 1) { 158 mid = (right + left) / 2; 159 if (intArray[mid] <= temp) 160 left = mid; 161 else 162 right = mid; 163 } 164 for (int j = flag; j > right; j--){ 165 intArray[j] = intArray[j - 1]; 166 } 167 intArray[right] = temp; 168 } 169 } 170 } 171 172 private static void selectSort(int[] intArray) { 173 int tmp = 0; 174 for (int i = 0; i < intArray.length; i++) { 175 tmp = intArray[i]; 176 for (int j = i + 1; j < intArray.length; j++) 177 if (tmp > intArray[j]) { 178 int temp = tmp; 179 tmp = intArray[j]; 180 intArray[j] = temp; 181 } 182 intArray[i] = tmp; 183 } 184 } 185 186 private static void print(int[] intArray) { 187 for(int i : intArray) { 188 System.out.print(i + " "); 189 } 190 System.out.println(); 191 } 192 193 private static void bubbleSort(int[] intArray) { 194 for(int i = 0; i < intArray.length; i++) 195 for(int j = 0; j < intArray.length - 1 - i; j++) 196 if(intArray[j] > intArray[j + 1]) 197 swap(intArray, j, j + 1); 198 } 199 200 private static void swap(int[] intArray, int i, int j) { 201 int tmp = intArray[i]; 202 intArray[i] = intArray[j]; 203 intArray[j] = tmp; 204 } 205 }

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轉載于:https://www.cnblogs.com/yongheng20/p/5748054.html

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