Java基础学习总结（28）——Java对各种排序算法的实现

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);
        }
    }
}

}