下面的算法它说mid 缺少局部定义。。求解

#include<stdio.h>
#include<stdlib.h>
#define N 5
typedef int KeyType;
typedef int ElemType;
struct SSTable
{
    ElemType *elem;
    int length;
};                                          
void Creat_Seq(SSTable &ST,ElemType r[],int n)
{       int i;                                          
    ST.elem=(ElemType*) calloc (n+1,sizeof(ElemType));
    if(!ST.elem)
        exit(0);
    for(i=1;i<=n;i++)
        ST.elem[i]=r[i-1];
    ST.length=n;
}
int Search_Seq(SSTable ST,KeyType key)                                       
{     
    int i=ST.length;
    ST.elem[0]=key;
    while(ST.elem[i]!=key)  --i;
    return i;
}
int Search_Bin(SSTable ST,KeyType key)
{
   

    int low,high,mid,i;
    int find=0;
    low=1; high=ST.length;
     if(mid%2==0)
    mid=(low+high)/2;
    if(mid%2==1)
        mid=(low+high+1)/2;
    while (low<=high&&find==0)
    {  if(mid%2==0)
    mid=((low+high)/2);
    if(mid%2==1)
        mid=(low+high+1)/2;
        if(key<ST.elem[mid] )
            high=mid-1;
        else if (key>ST.elem[mid])
            low=mid+1;
        else
        {
            i=mid;
            find=1;
        }
    }
    if(find==1)
        return i;
    else
        return 0;




}
void Traverse(SSTable ST)
{
    int i;
    for(i=1;i<=ST.length;i++)
        printf("%d  ",ST.elem[i]);
    return;
}
void main()
{
    ElemType r[N]={324,315,128,387,356};
    SSTable st;
    int i,j;
    long s;
    Creat_Seq(st,r,N);         //     由数组r产生顺序表静态查找表st     
    Traverse(st);                     //按顺序输出st
    printf("\n请输入查找的关键字:");
    scanf_s("%d",&s);
    printf("1:顺序查找法，  2：折半查找  ");
    scanf_s("%d",&j);
    {
        if(j==1)
              i=Search_Seq(st,s);
        if(j==2)
            i=Search_Bin(st,s);
        
    }
    if(i)
        printf("要查找的关键字的序号为%d\n",i);
    else
        printf("没找到\n");
    return;
}

使用了未初始化的局部变量“mid”

是未初始化，申明的时候他是个随机的值的。这个mid你是想作为中间值的吧。

int low,high,mid,i; // 开辟了内存的时候，这些变量都是随机的值来的，（课堂上老师叫他垃圾值，不喜欢大学老师的叫法）
     int find=0;
     low=1; high=ST.length;
 // 这个地方应该先给他赋值，比如 mid=(low+high)/2;
      if(mid%2==0)
     mid=(low+high)/2;