论坛 › C\C++交流 › malloc was not declared in this scope

18856966759 发表于 2019-12-13 11:52:49

malloc was not declared in this scope

红色的地方编译有错误，不知道哪里有问题
#include <stdio.h>
#define MAXSIZE 5
typedef int ElementType;
typedef int Position;
typedef struct LNode *List;
struct LNode{
        ElementType data;
        Position Last;/*保存数组Data[]中最后一个元素的位置*/
};


Position BinarySearch(List, ElementType);
int main()
{
        List L;
        L = (List)malloc(sizeof(struct LNode));
        L->data        = {12, 31, 55, 89, 101};
        L->Last = sizeof(L->data);
        ElementType X = 31;
        Position ret;
        ret = BinarySearch(L, X);
        printf("%d is %d", X, ret);
        return 0;
}

Position BinarySearch(List L, ElementType X)
{
        Position Left, Right, Mid;
       
        Left = 1;
        Right = L->Last;
        while(Left <= Right)
        {
                Mid = (Left + Right) / 2;
                if(L->data > X)
                        Right = Mid - 1;
                else if(L->data < X)
                        Left = Mid + 1;
                else
                        return Mid;
        }
}

superbe 发表于 2019-12-13 12:17:28

本帖最后由 superbe 于 2019-12-13 22:33 编辑

少头文件了吧#include <malloc.h>
BinarySearch的逻辑有点问题，修改的代码：

#include <stdio.h>
#include <malloc.h>
#define MAXSIZE 5
typedef int ElementType;
typedef int Position;
typedef struct LNode *List;
struct LNode {
    ElementType data;
    Position Last;
};

Position BinarySearch(List, ElementType);
int main()
{
    List L;
    L = (List)malloc(sizeof(struct LNode));
    //L->data = { 12, 31, 55, 89, 101 };
    L->data = 12;
    L->data = 31;
    L->data = 55;
    L->data = 89;
    L->data = 101;

    L->Last = sizeof(L->data) / sizeof(ElementType);
    ElementType X = 31;
    Position ret;
    ret = BinarySearch(L, X);
    (ret > 0) ? printf("%d is %d\n", X, ret) : printf("Not found\n");
    return 0;
}

Position BinarySearch(List L, ElementType X)
{
    Position Left, Right, Mid;

    Left = 1;
    Right = L->Last;
    while (Left <= Right)
    {
      Mid = (Left + Right) / 2;
      if (L->data == X)
            return Mid;
      if (L->data > X)
            Right = Mid - 1;
      else if (L->data < X)
            Left = Mid + 1;
    }
    return -1;
}

查看完整版本: malloc was not declared in this scope