數據結構與算法習題彙總(3)

Q:判斷一字符串是否爲迴文
A:對於這種要求輸入和輸出相反的情況，一般採用棧來解決，對於此題，只需將正序的字符串壓棧再將其全部彈出棧，判斷是否相同即可，代碼如下:

#include<stdio.h>
#include<stdlib.h>
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
#define MAXSIZE 100
typedef int status;
typedef char elemtype;
typedef struct stack{
    elemtype ch[MAXSIZE];
    int top;
}stack;

status visit(elemtype c){
    printf("%c ",c);
}

status initstack(stack *S){
    S->top=-1;
}

status stacklength(stack *S){
    return S->top+1;
}

status push(stack *S,elemtype data){
    S->top++;
    S->ch[S->top]=data;
}

status pop(stack *S,elemtype data){
    data=S->ch[S->top];
    S->top--;
}

status createstack(stack *S,elemtype start,elemtype end){
    int i=0;
    for(i=start;i<end;i++){
        S->top++;
        S->ch[S->top]=i;
    }
}

status createstack2(stack *S,elemtype data){
    S->top++;
    S->ch[S->top]=data; 
}

status traversestack(stack *S){
    for(int i=S->top;i>=0;i--){
        visit(S->ch[i]);
    }
    printf("\n");
}

status inversestack(stack *S,stack *S1){
    for(int i=S->top;i>=0;i--){
        if(S->ch[i]!=S1->ch[i])
            return FALSE;
        return TRUE;
    }
}

int main(void){
    stack S,S1;
    initstack(&S);
    initstack(&S1);
    createstack(&S,'a','z');
    for(char i='z';i>='a';i--){
        push(&S,i);
    }
    traversestack(&S);
    for(int i=S.top;i>=0;i--){
        push(&S1,S.ch[i]);
    }
    traversestack(&S);
    if(inversestack(&S,&S1))
        printf("迴文\n");
    else
        printf("不是迴文\n");
}

Q：藉助棧，將單鏈表逆置
A:再次強調對於要求輸入輸出相反的題目，首先考慮用棧解決，將鏈表中所有元素壓棧，再彈出棧即可，代碼如下：

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define ERROR 0
#define OK 1
#define TRUE 1
#define FALSE 0
#define maxsize 40
typedef int status; 
typedef int elemtype;

//創建鏈表 
struct node
{
    elemtype data;
    struct node *next;
}node;
typedef struct sqstack{
    elemtype data[maxsize];
    elemtype top;
}sqstack;
typedef struct node *linklist;

status visit(elemtype c)
 {
    printf("%d ",c);
    return OK;
 }

 //初始化鏈表
status initlist(linklist *l)
{
    (*l)=(linklist)malloc(sizeof(node));
    if(!(*l))
    return ERROR;
    (*l)->next=NULL;
    return OK;
}


//尾插法
status createlisttail(linklist *l,int n)
{
    linklist p=*l,q;
    int i;
    srand(time(0));
    for(i=0;i<n;i++)
    {
        q=(linklist)malloc(sizeof(node));
        q->data=rand()%100;
        p->next=q;
        p=q;
    }
    p->next=NULL;
    return OK;
 } 

status traverselist(linklist l)
 {
    linklist p=l->next;
    while(p)
    {
        visit(p->data);
        p=p->next;
    }
     printf("\n");
 }

 //將元素壓入棧 
status push(sqstack *s,elemtype data)
{
    if(s->top==maxsize-1){
        return ERROR;//判斷棧是否已滿 
    }
    else{
        s->top++;
        s->data[s->top]=data;
    }
    return OK;
}

//出棧並返回元素值 
status pop(sqstack *s){
    if(s->top==-1){
        return ERROR;
    }
    else{
        elemtype e;
        e=s->data[s->top];
        printf("%d ",e);
        s->top--;
    }
    return OK;
} 

 status traversestack(sqstack *s){
    int i=0;
    for(i=s->top;i>=0;i--){
        printf("%d ",s->data[i]);
    }
    printf("\n");
}

int main(void){
    linklist l; 
    sqstack S;
    initlist(&l);
    int num;
    scanf("%d",&num);
    createlisttail(&l,num); 
    printf("整體創建l的元素（尾插法）\n");
    traverselist(l);
    linklist pmove=l->next;
    while(pmove){
        push(&S,pmove->data);
        pmove=pmove->next;
    }
    for(int i=0;i<num;i++){
        pop(&S);
    }
} 

Q;實現雙棧共享空間的出入棧算法
A:見拙作《雙棧共用存儲空間》，不再贅述