mergsort.c

时间复杂度O(n)

 

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-->#include <stdio.h>
#include <stdlib.h>

void merge_sort_inner(int A[], int p, int r)
{
    int q, i, j, k, n1, n2;
    int temp, *L, *R;
    if(p < r)
    {
        q = (p + r) / 2;
        merge_sort_inner(A, p, q);
        merge_sort_inner(A, q+1, r);
        n1 = q - p + 1;
        n2 = r - q;

        L = (int*)malloc(sizeof(int) * (n1+1));
        R = (int*)malloc(sizeof(int) * (n2+1));
        for(i = 0; i < n1; i ++)
            L[i] = A[p + i];
        for(i = 0; i < n2; i ++)
            R[i] = A[q + i + 1];
        L[n1] = R[n2] = 2147483647;
        i = 0;
        j = 0;

        for(k = p; k <= r; k ++)
            if(L[i] <= R[j])
                A[k] = L[i++];
            else
                A[k] = R[j++];
        free(L);
        free(R);
    }
}

void merge_sort(int A[], int n)
{
    merge_sort_inner(A, 0, n - 1);
}


int main()
{
    int A[] = {3, 7 ,2, 0, 1,3, 2};
    int i;
    merge_sort(A, 7);
    for(i = 0; i < 7; i ++)
        printf("%d ", A[i]);
    printf("
");
    system("pause");
    return 0;
}