Java基础学习总结（28）——Java对各种排序算法的实现

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这里总结下各种排序算法的java实现
冒泡排序
public class BubbleSort {

publicstaticint[] bubbleSort(int[] array) {      if(array == null) {          returnnull;     }     for(inti = 0; i < array.length; i++) {          for(intj = i + 1; j < array.length; j++) {              if(array[i] > array[j]) {                  array[i] = array[i] + array[j];                  array[j] = array[i] - array[j];                  array[i] = array[i] - array[j];              }         }     }     returnarray; }

}
插入排序
public class InsertSort {

publicstaticint[] insertSort(int[] array) {      if(array == null) {          returnnull;     }     for(inti = 1; i < array.length; i++) {          for(intj = i; (j > 0) && (array[j] < array[j - 1]); j--) {              SortUtils.swap(array, j, j - 1);         }     }     returnarray; }

}

选择排序
public class SelectionSort {

publicstaticint[] selectionSort(int[] array) {      if(array == null) {          returnnull;     }     for(inti = 0; i < array.length; i++) {          intlowIndex = i;          for(intj = array.length - 1; j > i; j--) {              if(array[j] < array[lowIndex]) {                  lowIndex = j;              }         }         SortUtils.swap(array, i, lowIndex);      }     returnarray; }

}

?
Shell排序
public class ShellSort {

publicstaticint[] shellSort(int[] array) {      if(array == null) {          returnnull;     }     for(inti = array.length / 2; i > 2; i /= 2) {          for(intj = 0; j < i; j++) {              insertSort(array, j, i);          }     }     insertSort(array,0,1);     returnarray; } privatestaticvoidinsertSort(int[] array, intstart,intinc) {      for(inti = start + inc; i < array.length; i += inc) {          for(intj = i; (j >= inc) && (array[j] < array[j - inc]); j -= inc) {              SortUtils.swap(array, j, j - inc);          }     } }

}

?
快速排序
public class QKSort {

publicstaticint[] quickSort(int[] array) {      if(array != null) {          returnquickSort(array,0, array.length - 1);     }     returnnull; } privatestaticint[] quickSort(int[] array, intbeg,intend) {      if(beg >= end || array == null) {          returnnull;     }     intp = partition(array, beg, end);      quickSort(array, beg, p - 1);     quickSort(array, p + 1, end);      returnarray; } /** * 找到分界点  * @param array  * @param beg  * @param end  * @return  */ privatestaticintpartition(int[] array, intbeg,intend) {      intlast = array[end];      inti = beg - 1;     for(intj = beg; j <= end - 1; j++) {          if(array[j] <= last) {              i++;             if(i != j) {                  array[i] = array[i] ^ array[j];                  array[j] = array[i] ^ array[j];                  array[i] = array[i] ^ array[j];              }         }     }     if((i + 1) != end) {          array[i + 1] = array[i + 1] ^ array[end];          array[end] = array[i + 1] ^ array[end];          array[i + 1] = array[i + 1] ^ array[end];      }     returni + 1; }

}

堆排序
public class HeapSort {

publicstaticint[] heapSort(int[] array) {      if(array == null) {          returnnull;     }     MaxHeap h = newMaxHeap();     h.init(array);     for(inti = 0; i < array.length; i++) {          h.remove();     }     System.arraycopy(h.queue,1, array, 0, array.length);      returnarray; } privatestaticclassMaxHeap {      voidinit(int[] data) {          this.queue = newint[data.length + 1];         for(inti = 0; i < data.length; i++) {              queue[++size] = data[i];              fixUp(size);         }     }     privateintsize = 0;     privateint[] queue;      publicintget() {          returnqueue[1];     }     publicvoidremove() {          SortUtils.swap(queue,1, size--);          fixDown(1);     }     // fixdown      privatevoidfixDown(intk) {          intj;         while((j = k << 1) <= size) {              if(j < size && queue[j] < queue[j + 1]) {                  j++;             }             // 不用交换              if(queue[k] > queue[j]) {                  break;             }             SortUtils.swap(queue, j, k);              k = j;          }     }     privatevoidfixUp(intk) {          while(k > 1) {              intj = k >> 1;             if(queue[j] > queue[k]) {                  break;             }             SortUtils.swap(queue, j, k);              k = j;          }     } }

}

归并排序
public class MergeSort {

publicstaticint[] mergeSort(int[] array) {      if(array == null) {          returnnull;     }     int[] temp = newint[array.length];     returnmergeSort(array, temp, 0, array.length - 1); } privatestaticint[] mergeSort(int[] array, int[] temp, intl,intr) {      intmid = (l + r) / 2;     if(l == r) {          returnnull;     }     mergeSort(array, temp, l, mid);      mergeSort(array, temp, mid + 1, r);      for(inti = l; i <= r; i++) {          temp[i] = array[i];      }     inti1 = l;      inti2 = mid + 1;     for(intcur = l; cur <= r; cur++) {          if(i1 == mid + 1) {              array[cur] = temp[i2++];          }elseif(i2 > r) {              array[cur] = temp[i1++];          }elseif(temp[i1] < temp[i2]) {              array[cur] = temp[i1++];          }else{             array[cur] = temp[i2++];          }     }     returnarray; }

}

归并排序(改进)
public class MergeSortImproved {

privatestaticfinalint THRESHOLD = 10; publicstaticint[] mergeSort(int[] array) {      if(array == null) {          returnnull;     }     int[] temp = newint[array.length];     returnmergeSort(array, temp, 0, array.length - 1); } privatestaticint[] mergeSort(int[] array, int[] temp, intl,intr) {      inti, j, k;      intmid = (l + r) / 2;     if(l == r) {          returnnull;     }     if((mid - l) >= THRESHOLD) {          mergeSort(array, temp, l, mid);      }else{         insertSort(array, l, mid - l + 1);     }     if((r - mid) > THRESHOLD) {          mergeSort(array, temp, mid + 1, r);      }else{         insertSort(array, mid + 1, r - mid);      }     for(i = l; i <= mid; i++) {          temp[i] = array[i];      }     for(j = 1; j <= r - mid; j++) {          temp[r - j + 1] = array[j + mid];      }     inta = temp[l];      intb = temp[r];      for(i = l, j = r, k = l; k <= r; k++) {          if(a < b) {              array[k] = temp[i++];              a = temp[i];          }else{             array[k] = temp[j--];              b = temp[j];          }     }     returnarray; } privatestaticvoidinsertSort(int[] array, intstart,intlen) {      for(inti = start + 1; i < start + len; i++) {          for(intj = i; (j > start) && array[j] < array[j - 1]; j--) {              SortUtils.swap(array, j, j - 1);         }     } }

}

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