[英]global variable problem
我声明一个全局变量,并在函数中使用和修改其值。 然后我想获取此全局变量的修改后的值,它有一些问题。 谁能帮我?
#include<stdio.h>
#include<string.h>
#include<conio.h>
#include<stdlib.h>
#define MAX 10
struct link
{
int freq;
char value[MAX];
struct link* right;
struct link* left;
};
typedef struct link node;
void sort(node *[], int);
node* create(char[], int);
void sright(node *[], int);
void Assign_Code(node*, int [], int);
void Delete_Tree(node *);
int test[720][720];
main()
{
node* ptr, * head;
int i, n, total = 0, u, c[256];
char str[MAX];
node* a[256];
int freq;
printf( "Huffman Algorithm\n");
printf("\nEnter the no. of letter to be coded:");
/*input the no. of letters*/
scanf("%d", &n);
for (i = 0; i < n; i++)
{
printf("Enter the letter & frequency:");
/*input the letter & frequency*/
scanf("%s %d", str, &freq);
a[i] = create(str, freq);
}
while (n > 1)
{
sort(a, n);
u = a[0]->freq + a[1]->freq;
strcpy(str,a[0]->value);
strcat(str,a[1]->value);
ptr = create(str, u);
ptr->right = a[1];
ptr->left = a[0];
a[0] = ptr;
sright(a, n);
n--;
}
Assign_Code(a[0], c, 0);
//getch();
printf("Code: ");
for (i = 1; i <= n; i++)
{
printf("%d", test[0][i]);
}
printf("\n");
Delete_Tree(a[0]);
}
node* create(char a[], int x)
{
node* ptr;
ptr = (node *) malloc(256*sizeof(node));
ptr->freq = x;
strcpy( ptr->value , a);
ptr->right = ptr->left = NULL;
return(ptr);
}
void sort(node* a[], int n)
{
int i, j;
node* temp;
for (i = 0; i < n - 1; i++)
for (j = i; j < n; j++)
if (a[i]->freq > a[j]->freq)
{
temp = a[i];
a[i] = a[j];
a[j] = temp;
}
}
void sright(node* a[], int n)
{
int i;
for (i = 1; i < n - 1; i++)
a[i] = a[i + 1];
}
void Assign_Code(node* tree, int c[], int n)
{
int i;
if ((tree->left == NULL) && (tree->right == NULL))
{
printf("%s code: ", tree->value);
test[0][0]=tree->value;
for (i = 0; i < n; i++)
{
test[0][i+1]=c[i];
printf("%d", c[i]);
}
printf("\n");
}
else
{
c[n] = 1;
n++;
Assign_Code(tree->left, c, n);
c[n - 1] = 0;
Assign_Code(tree->right, c, n);
}
}
void Delete_Tree(node * root)
{
if(root!=NULL)
{
Delete_Tree(root->left);
Delete_Tree(root->right);
free(root);
}
}
让我强调一下问题:
while (n > 1)
{
...
n--;
}
...
for (i = 1; i <= n; i++)
{
printf("%d", test[0][i]);
}
到第二个循环开始时, n
为1,并且printf
仅执行一次,因此仅输出test[0][1]
的值。
test[0][1]
的值在Assign_Code
被多次重写(与树中的叶节点数一样多):
void Assign_Code(node* tree, int c[], int n)
{
if ((tree->left == NULL) && (tree->right == NULL))
{
...
for (i = 0; i < n; i++)
{
test[0][i+1]=c[i];
}
}
...
}
现在,由于您遍历树的方式,最后一次覆盖test[0][1]
是针对第一个字符为“ 0”的霍夫曼代码的。
you can store the n value to some temporary variables, after you get the
价值观。
Then use the temporary variable in your for loop condition.
scanf("%d", &n);
int temp = n ;
for (i = 1; i <= temp ; i++)
{
printf("%d", test[0][i]);
}
附带说明:
node* create(char a[], int x)
{
node* ptr;
ptr = (node *) malloc(256*sizeof(node)); // <--- This is wrong
ptr->freq = x;
strcpy( ptr->value , a);
ptr->right = ptr->left = NULL;
return(ptr);
}
没有理由分配256倍的节点大小来存储一个节点。 您正在创建一个节点,并将其存储在指向节点的指针数组中。 在那里分配一个节点,如下所示:
malloc (sizeof (node)); or malloc ((sizeof (*ptr));
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