fig07_12.cpp

来自「经典书籍源代码啊。。。第三版。。。数据结构与算法分析——C++描述(第3版).」· C++ 代码 · 共 34 行

/**
 * Internal method that merges two sorted halves of a subarray.
 * a is an array of Comparable items.
 * tmpArray is an array to place the merged result.
 * leftPos is the left-most index of the subarray.
 * rightPos is the index of the start of the second half.
 * rightEnd is the right-most index of the subarray.
 */
template <typename Comparable>
void merge( vector<Comparable> & a, vector<Comparable> & tmpArray,
            int leftPos, int rightPos, int rightEnd )
{
    int leftEnd = rightPos - 1;
    int tmpPos = leftPos;
    int numElements = rightEnd - leftPos + 1;

    // Main loop
    while( leftPos <= leftEnd && rightPos <= rightEnd )
        if( a[ leftPos ] <= a[ rightPos ] )
            tmpArray[ tmpPos++ ] = a[ leftPos++ ];
        else
            tmpArray[ tmpPos++ ] = a[ rightPos++ ];

    while( leftPos <= leftEnd )    // Copy rest of first half
        tmpArray[ tmpPos++ ] = a[ leftPos++ ];

    while( rightPos <= rightEnd )  // Copy rest of right half
        tmpArray[ tmpPos++ ] = a[ rightPos++ ];

    // Copy tmpArray back
    for( int i = 0; i < numElements; i++, rightEnd-- )
        a[ rightEnd ] = tmpArray[ rightEnd ];
}