快速排序模板

伪代码(算法导论（原书第3版）P95)：

QUICKSORT(A, p, r)　　//A为数组，若需排序数组A全部元素，即QUICKSORT(A, 1, A.length)

1 if p < r
2     q = PARTITION(A, p, r)
3     QUICKSORT(A, p, q-1)
4     QUICKSORT(A, q+1, r)

PARTITION(A, p, r)

1 x = A[r]
2 i = p-1
3 for j = p to r-1
4     if A[j] <= x
5         i = i+1
6         exchange A[i] with A[j]
7 exchange A[i+1] with A[r]
8 return i + 1

随机化：

RANDOMIZED-PARTITION(A, p, r)

1 i = RANDOM(p, r)
2 exchange A[r] with A[i]
3 return PARTITION(A, p, r)

RANDOMIZED-QUICKSORT(A, p, r)

1 if p < r
2     q = RANDOMIZED-PARTITION(A, p, r)
3     QUICKSORT(A, p, q-1)
4     QUICKSORT(A, q+1, r)

C++:

void Quicksort(int a[], int l, int r){
    if(l < r){
        int p = Partition(a, l, r);
        Quicksort(a, l, p-1);
        Quicksort(a, p+1, r);
    }
}

int Partition(int a[], int l, int r){
    int x = a[r];
    int i = l-1;
    for(int j = l; j <= r-1; j++){
        if(a[j] <= x){
            i++;
            swap(a[i], a[j]);
        }
    }
    swap(a[i+1], a[r]);
    return i+1;
}

posted on 2022-04-23 10:47 我欲阅读(78) 评论(0) 收藏举报