[英]c passing pointer to recursive function
So here i am struggling with this program, i was trying to find out how can I use a array of pointers declared into main, in a recursive function to memorize data, the question that arises here is if it's the same approach as for a single pointer, what about for a struct type ? 所以在这里我正在努力学习这个程序,我试图找出如何使用一个声明为main的指针数组,在一个递归函数中记忆数据,这里出现的问题是,如果它与单个方法相同指针,结构类型怎么样? what is the best way to pass by reference a variable/array to a recursive function ?
通过引用变量/数组传递给递归函数的最佳方法是什么?
#include <stdio.h>
#include <stdlib.h>
#define N 1
void f(int i,int j,int *cnt);
int j=0;
int main(int argc, char *argv[])
{
int *cnt=0;
f(0,++j,&cnt);
printf("------ %d ---- \n",cnt);
system("PAUSE");
return 0;
}
void f(int i,int j,int *cnt){
if(i>N){
printf("---if --- %d ---- %d \n",i,j);
(*cnt)++;
return;
}
(*cnt)++;
printf("---bg --- %d ---- %d \n",i,j);
f(i+1,++j,cnt);
f(i+1,++j,cnt);
}
Another thing i'd like to know is how does the recursive functions handle the ++i and i++ and i+1 increments (when passed as parameters), 另一件我想知道的是递归函数如何处理++ i和i ++以及i + 1增量(当作为参数传递时),
int main(int argc, char *argv[])
{
int *cnt=0;
f(0,++j,&cnt);
printf("------ %d ---- \n",(*cnt));
system("PAUSE");
return 0;
}
needs to be 需要是
int main(int argc, char *argv[])
{
int intStorage = 0;//<---- As Oli said.
int *cnt= &intStorage;
f(0,++j,cnt);//<-------AMPERSAND removed, overly dereferenced.
printf("------ %d ---- \n",(*cnt));
system("PAUSE");
return 0;
}
++i and i++ and i+1 (when passed as parameters): ++ i和i ++和i + 1(当作为参数传递时):
I'll try and fix your function a little too: 我会尝试修复你的功能:
void f(int i,int j,int *cnt){
if(i>N){
printf("---if --- %d ---- %d \n",i,j);
return;
}
(*cnt)++;
printf("---bg --- %d ---- %d \n",i,j);
if ( i < 50 && j < 50 ) {
f(i+1,++j,cnt);
f(i+1,++j,cnt);
}
}
Still a lot of recursion but without the danger of not stopping. 仍然有很多递归,但没有不停止的危险。
A simple way of handling the pointer into your function is: 处理指向函数的指针的简单方法是:
#include <stdio.h>
#include <stdlib.h>
#define N 1
void f(int i, int j, int *cnt);
int j = 0;
int main(void)
{
int cnt = 0;
f(0, ++j, &cnt);
printf("------ %d ----\n", cnt);
return 0;
}
void f(int i, int j, int *cnt)
{
// Having a local variable j and a global j is likely to confuse someone!
if (i > N)
{
printf("---if --- %d ---- %d\n", i, j);
return;
}
(*cnt)++;
printf("---bg --- %d ---- %d\n", i, j);
f(i+1, ++j, cnt);
f(i+1, ++j, cnt);
}
This code produces the following output with no crash: 此代码生成以下输出而不会崩溃:
---bg --- 0 ---- 1
---bg --- 1 ---- 2
---if --- 2 ---- 3
---if --- 2 ---- 4
---bg --- 1 ---- 3
---if --- 2 ---- 4
---if --- 2 ---- 5
------ 3 ----
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