順序尋找 sequential find

#include <stdio.h>#include <stdlib.h>typedef int KeyType;struct ElemType{    int key;};int find_seq(struct ElemType arr[],int n,KeyType key){    int i=0;    for(;i<n;i++){        if(arr[i].key==key)return i;        printf("check %d\n",arr[i]);    }    return -1;}//較好的提高，for迴圈裡只有一個判斷，注意資料不能越界int find_seq_improved(struct ElemType arr[],int n,KeyType key){    int i=0;    arr[n].key=key; //設定崗哨    for(;;i++){        if(arr[i].key==key) break;        printf("check %d\n",arr[i]);    }    if(i<n)return i;    else return -1;}int main(){    struct ElemType arr[10];    arr[0].key=0;    arr[1].key=11;    arr[2].key=22;    arr[3].key=33;    arr[4].key=44;    arr[5].key=55;    int idx=find_seq(arr,6,554);    printf("idx=%d\n",idx);    int idx1=find_seq_improved(arr,6,554);    printf("idx=%d\n",idx1);    return 0;}