Data Structures and Algorithm Analysis in C 學習之List反轉

方法1:

// problem 3.12.a
List Reverse_a(List L)
{
    List TmpL;
    Position P;

    P = First(L);
    TmpL = MakeEmpty();
    while ( P != NULL ) {
        Insert(Retrieve(P), TmpL, TmpL);
        P = Advance(P);
    }

    DeleteList(L);
    return TmpL;
}

方法2:

// problem 3.12.b
List Reverse(List L)
{
    Position P, PPrev, PNext;

    P = First(L);
    PPrev = L;
    PNext = Advance(P);

    if(P == NULL)
        return L;

    while(PNext != NULL) {
        P->Next = PPrev;
        if(PPrev == L)
            P->Next = NULL;

        PPrev = P;
        P = PNext;
        PNext = Advance(P);
    }

    P->Next = PPrev;
    L->Next = P;

    return L;
}

測試代碼

#include "list.h"
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char* argv[])
{
    List L;
    Position P;
    int i;

    L = MakeEmpty();
    for(i = 0; i < 10; i++)
        Insert(i, L, L);

    PrintList(L);
    L = Reverse(L);
    PrintList(L);
}