java 查找算法
// binarySearch.java
// demonstrates recursive binary search
// to run this program: C>java BinarySearchApp
////////////////////////////////////////////////////////////////
class ordArray
{
private long[] a; // ref to array a
private int nElems; // number of data items
//-----------------------------------------------------------
public ordArray(int max) // constructor
{
a = new long[max]; // create array
nElems = 0;
}
//-----------------------------------------------------------
public int size()
{ return nElems; }
//-----------------------------------------------------------
public int find(long searchKey)
{
return recFind(searchKey, 0, nElems-1);
}
//-----------------------------------------------------------
private int recFind(long searchKey, int lowerBound,
int upperBound)
{
int curIn;
curIn = (lowerBound + upperBound ) / 2;
if(a[curIn]==searchKey)
return curIn; // found it
else if(lowerBound > upperBound)
return nElems; // can't find it
else // divide range
{
if(a[curIn] < searchKey) // it's in upper half
return recFind(searchKey, curIn+1, upperBound);
else // it's in lower half
return recFind(searchKey, lowerBound, curIn-1);
} // end else divide range
} // end recFind()
//-----------------------------------------------------------
public void insert(long value) // put element into array
{
int j;
for(j=0; j<nElems; j++) // find where it goes
if(a[j] > value) // (linear search)
break;
for(int k=nElems; k>j; k--) // move bigger ones up
a[k] = a[k-1];
a[j] = value; // insert it
nElems++; // increment size
} // end insert()
//-----------------------------------------------------------
public void display() // displays array contents
{
for(int j=0; j<nElems; j++) // for each element,
System.out.print(a[j] + " "); // display it
System.out.println("");
}
//-----------------------------------------------------------
} // end class ordArray
////////////////////////////////////////////////////////////////
class BinarySearchApp
{
public static void main(String[] args)
{
int maxSize = 100; // array size
ordArray arr; // reference to array
arr = new ordArray(maxSize); // create the array
arr.insert(72); // insert items
arr.insert(90);
arr.insert(45);
arr.insert(126);
arr.insert(54);
arr.insert(99);
arr.insert(144);
arr.insert(27);
arr.insert(135);
arr.insert(81);
arr.insert(18);
arr.insert(108);
arr.insert(9);
arr.insert(117);
arr.insert(63);
arr.insert(36);
arr.display(); // display array
int searchKey = 27; // search for item
if( arr.find(searchKey) != arr.size() )
System.out.println("Found " + searchKey);
else
System.out.println("Can't find " + searchKey);
} // end main()
} // end class BinarySearchApp
////////////////////////////////////////////////////////////////
// mergeSort.java
// demonstrates recursive merge sort
// to run this program: C>java MergeSortApp
////////////////////////////////////////////////////////////////
class DArray
{
private long[] theArray; // ref to array theArray
private int nElems; // number of data items
//-----------------------------------------------------------
public DArray(int max) // constructor
{
theArray = new long[max]; // create array
nElems = 0;
}
//-----------------------------------------------------------
public void insert(long value) // put element into array
{
theArray[nElems] = value; // insert it
nElems++; // increment size
}
//-----------------------------------------------------------
public void display() // displays array contents
{
for(int j=0; j<nElems; j++) // for each element,
System.out.print(theArray[j] + " "); // display it
System.out.println("");
}
//-----------------------------------------------------------
public void mergeSort() // called by main()
{ // provides workspace
long[] workSpace = new long[nElems];
recMergeSort(workSpace, 0, nElems-1);
}
//-----------------------------------------------------------
private void recMergeSort(long[] workSpace, int lowerBound,
int upperBound)
{
if(lowerBound == upperBound) // if range is 1,
return; // no use sorting
else
{ // find midpoint
int mid = (lowerBound+upperBound) / 2;
// sort low half
recMergeSort(workSpace, lowerBound, mid);
// sort high half
recMergeSort(workSpace, mid+1, upperBound);
// merge them
merge(workSpace, lowerBound, mid+1, upperBound);
} // end else
} // end recMergeSort()
//-----------------------------------------------------------
private void merge(long[] workSpace, int lowPtr,
int highPtr, int upperBound)
{
int j = 0; // workspace index
int lowerBound = lowPtr;
int mid = highPtr-1;
int n = upperBound-lowerBound+1; // # of items
while(lowPtr <= mid && highPtr <= upperBound)
if( theArray[lowPtr] < theArray[highPtr] )
workSpace[j++] = theArray[lowPtr++];
else
workSpace[j++] = theArray[highPtr++];
while(lowPtr <= mid)
workSpace[j++] = theArray[lowPtr++];
while(highPtr <= upperBound)
workSpace[j++] = theArray[highPtr++];
for(j=0; j<n; j++)
theArray[lowerBound+j] = workSpace[j];
} // end merge()
//-----------------------------------------------------------
} // end class DArray
////////////////////////////////////////////////////////////////
class MergeSortApp
{
public static void main(String[] args)
{
int maxSize = 100; // array size
DArray arr; // reference to array
arr = new DArray(maxSize); // create the array
arr.insert(64); // insert items
arr.insert(21);
arr.insert(33);
arr.insert(70);
arr.insert(12);
arr.insert(85);
arr.insert(44);
arr.insert(3);
arr.insert(99);
arr.insert(0);
arr.insert(108);
arr.insert(36);
arr.display(); // display items
arr.mergeSort(); // merge sort the array
arr.display(); // display items again
} // end main()
} // end class MergeSortApp
////////////////////////////////////////////////////////////////