非递归函数的递归求解

[code] #include <stdio.h>

#include <math.h>

#include <stdlib.h>

#define STACK_INIT_SIZE 20

#define STACKINCREMENT 10

 typedefint ElemType;

typedef struct{

 ElemType *base;

 ElemType *top;

 int stacksize;

} sqStack;

/*初始化栈*/

void initStack(sqStack *s)

{

 /*内存中开辟一段连续空间作为栈空间，首地址赋值给s->base*/

 s->base = (ElemType *)malloc(STACK_INIT_SIZE * sizeof(ElemType));

 if(!s->base) exit(0);/*分配空间失败*/

 s->top = s->base;/*最开始，栈顶就是栈底*/

 s->stacksize = STACK_INIT_SIZE; /*最大容量为STACK_INIT_SIZE */

}

/*入栈操作，将e压入栈中*/

 void Push(sqStack *s, ElemType e){

 if(s->top - s->base >= s->stacksize){

 /*栈满，追加空间*/

 s->base = (ElemType *)realloc(s->base, (s->stacksize +

 STACKINCREMENT) * sizeof(ElemType));

 if(!s->base) exit(0);/*存储分配失败*/

 s->top = s->base + s->stacksize;

 s->stacksize = s->stacksize + STACKINCREMENT;/*设置栈的最大容量*/

}

 *(s->top) = e; /*放入数据*/

 s->top++;

}

/*出栈操作，用e将栈顶元素返回*/

 void Pop(sqStack *s , ElemType *e){

 if(s->top == s->base) return;

 *e = *--(s->top);

}

int f(int n)

{

 int r = 1, e;

 sqStack stack;

 initStack(&stack);/*初始化栈*/

 while(n != 0){

 Push(&stack, n);/*保存现场n*/

 n = n / 2;

}

 while(stack.top != stack.base)

{

 Pop(&stack, &e);

 r = r * e;

}

 return r;

}

int main()

{

 printf("The result for conversion of recursion to non recursion is\n");

 printf("f(5)=%d \n", f(5));

 return 0;

}