help me with this programme

This is a discussion on help me with this programme within the C++ Programming forums, part of the General Programming Boards category; i write this programme to find the Kth number in the vector a the algorithms just like the quick sort ...

  1. #1
    Registered User
    Join Date
    Jun 2008
    Posts
    7

    help me with this programme

    i write this programme to find the Kth number in the vector a
    the algorithms just like the quick sort

    but it doesnot work right

    Code:
    void quickSelect(vector<int> & a, int left=0, int right=a.size(), int k) {
    
    	int middle = (left + right) / 2;
    	Comparable pivot = a[middle];
    	int i = left, j = right;
    	for (;;) {
    		while (a[i] < pivot) {
    			i = i + 1;
    		}
    		while (a[j] > pivot) {
    			j = j - 1;
    		}
    
    		if (i < j) {
    			swap(a[i], a[j]);
    			i = i + 1;
    			j = j - 1;
    		} else
    			break;
    	}
    	a[i+1] = pivot;
    
    	if (k <= i)
    		quickSelect(a, left, i - 1, k);
    	else if (k > i + 1)
    		quickSelect(a, i + 1, right, k - i);
    	else
    		cout << "the " << k << "th number is " << pivot << endl;
    }

  2. #2
    Registered User
    Join Date
    Dec 2006
    Location
    Canada
    Posts
    3,183
    1. Write a more descriptive subject next time (your subject fits pretty much all threads here)
    2. Need more detail. What do you mean it doesn't work? doesn't compile? (post compiler erros) doesn't run? (what happens) doesn't give you the result you expect? (provide the input, output, and expected output)

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