c - 反转字符串的顺序

Question

这是一个c程序，用于反转句子中单词的顺序(使用堆栈)作为输入读取，但我所能得到的只是句子中每个单词的相反顺序。如何反转句子(用“”或“,”分隔)？

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>

// A structure to represent a stack
struct Stack
{
    int top;
    unsigned capacity;
    char* array;
};

struct Stack* createStack(unsigned capacity)
{
    struct Stack* stack = (struct Stack*) malloc(sizeof(struct Stack));
    stack->capacity = capacity;
    stack->top = -1;
    stack->array = (char*) malloc(stack->capacity * sizeof(char));
    return stack;
}


int isFull(struct Stack* stack)
{   return stack->top == stack->capacity - 1; }

// Stack is empty when top is equal to -1
int isEmpty(struct Stack* stack)
{   return stack->top == -1;  }

// Function to add an item to stack.  It increases top by 1
void push(struct Stack* stack, char item)
{
    if (isFull(stack))
        return;
    stack->array[++stack->top] = item;
}

char pop(struct Stack* stack)
{
    if (isEmpty(stack))
        return 0;
    return stack->array[stack->top--];
}

// A stack based function to reverese a string
void reverse(char str[])
{
    int n = strlen(str);
    struct Stack* stack = createStack(n);

    // Push all characters of string to stack
    int i;
    for (i = 0; i < n; i++)
        push(stack, str[i]);

    for (i = 0; i < n; i++)

        str[i] = pop(stack);
}

int main()
{
    char str[50];
    fgets(str, sizeof(str), stdin);
    str[strlen(str)-1]='\0';


    reverse(str);
    printf("Reversed string is %s", str);

    return 0;
}

Answer 1

试试这个代码

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>

// A structure to represent a stack

struct Stack
{
    int top;
    unsigned capacity;
    //char* array;
    char** array;
};

struct Stack* createStack(unsigned capacity)
{
    if( capacity < 1 )
    {
        capacity = 1;
    }
    struct Stack* stack = (struct Stack*) malloc(sizeof(struct Stack));
    stack->capacity = capacity;
    stack->top = -1;
    stack->array = (char**) malloc(stack->capacity * sizeof(char*));
    return stack;
}



void resizeStack( struct Stack* stack , int new_size ) 
{
    if( NULL != stack && new_size > stack->capacity )  // Only support expansion 
    {
        char ** old_array = stack->array ;
        stack->array = (char**) malloc(new_size * sizeof(char*));
        memcpy(stack->array,old_array,stack->capacity * sizeof(char*));
        free(old_array);
        stack->capacity = new_size ;
    }
}
int isFull(struct Stack* stack)
{   return stack->top == stack->capacity - 1; }

// Stack is empty when top is equal to -1
int isEmpty(struct Stack* stack)
{   return stack->top == -1;  }


// Function to add an item to stack.  It increases top by 1
void push(struct Stack* stack, char *item)
{
    if ( isFull(stack) )
    {
        resizeStack(stack, stack->capacity * 2 );
    }
    stack->array[++stack->top] =(char *) malloc(sizeof(char)*(strlen(item) +1));

    strcpy(stack->array[stack->top] , item);
}

char * pop(struct Stack* stack)
{
    char * ret = NULL;
    if(! isEmpty(stack) )
    {
        ret = stack->array[stack->top];
        stack->array[stack->top] = NULL ;
        stack->top --;
    }
    return ret;
}

void freeStack(struct Stack* stack)
{
    if( NULL != stack && NULL != stack->array ) 
    {
        while( ! isEmpty(stack) ) 
        {
           free(pop(stack));
        }
        free(stack->array);
    }
    else 
    {
        printf(" freeStack try to free NULL ");
    }
}

#define SEPARATER ' '

// A stack based function to reverese a string
void reverse(char str[])
{
    int n = strlen(str);
    struct Stack* stack = createStack(4);
    char sep[2];
    sep[0] = SEPARATER;
    sep[1] = 0 ;
    char * pch = strtok(str,sep);
    while( NULL != pch )
    {
        push(stack,pch);
        pch = strtok(NULL,sep); 
    }

    char * swap_buff = (char*)malloc((n+1) * sizeof(char));
    char * cp_buff = swap_buff;
    do
    {
        char * top = pop(stack);
        strcpy(cp_buff , top);
        cp_buff += strlen(top);
        *cp_buff++ = SEPARATER;

    }while( ! isEmpty(stack) );
    swap_buff[n] = 0;
    strcpy(str,swap_buff);
    freeStack(stack);
}

int main()
{
    char str[50];
    fgets(str, sizeof(str), stdin);
    str[strlen(str)-1]='\0';

    reverse(str);
    printf("Reversed string is %s\n", str);

    return 0;
}