实验五
ex1_1:
#include <stdio.h> const int N=5; int binarySearch(int x[], int n, int item); int main() { int a[N]={1,3,9,16,21}; int i,index, key; printf("数组a中的数据:\n"); for(i=0;i<N;i++) printf("%d ",a[i]); printf("\n"); printf("输入待查找的数据项: "); scanf("%d", &key); index=binarySearch(a,N,key); if(index>=0) printf("%d在数组中,下标为%d\n", key, index); else printf("%d不在数组中\n", key); return 0; } int binarySearch(int x[], int n, int item) { int low, high, mid; low = 0; high = n-1; while(low <= high) { mid = (low+high)/2; if (item == x[mid]) return mid; else if(item < x[mid]) high = mid - 1; else low = mid + 1; } return -1; }
ex1_2:
#include <stdio.h> const int N=5; int binarySearch(int *x, int n, int item); int main() { int a[N]={1,3,9,16,21}; int i,index, key; printf("数组a中的数据:\n"); for(i=0;i<N;i++) printf("%d ",a[i]); printf("\n"); printf("输入待查找的数据项: "); scanf("%d", &key); index=binarySearch(a,N,key); if(index>=0) printf("%d在数组中,下标为%d\n", key, index); else printf("%d不在数组中\n", key); return 0; } int binarySearch(int *x, int n, int item) { int low, high, mid; low = 0; high = n-1; while(low <= high) { mid = (low+high)/2; if (item == *(x+mid)) return mid; else if(item < *(x+mid)) high = mid - 1; else low = mid + 1; } return -1;
ex2_2:
#include <stdio.h> #include <string.h> void selectSort(char str[][20], int n ); int main() { char name[][20] = {"John", "Alex", "Joseph", "Candy", "Geoge"}; int i; printf("输出初始名单:\n"); for(i=0; i<5; i++) printf("%s\n", name[i]); selectSort(name, 5); printf("按字典序输出名单:\n"); for(i=0; i<5; i++) printf("%s\n", name[i]); return 0; } void selectSort(char str[][20], int n) { int i, j, k; char temp[20]; for(i=0; i<n-1; i++) { k = i; for(j=i+1; j<n; j++) if (strcmp(str[j],str[k])<0) k = j; if(k != i) { strcpy(temp,str[i]); strcpy(str[i],str[k]); strcpy(str[k],temp); } } }
二分查找又称折半查找,优点是比较次数少,查找速度快,平均性能好;其缺点是要求待查表为有序表,且插入删除困难。因此,折半查找方法适用于不经常变动而查找频繁的有序列表。首先,假设表中元素是按升序排列,将表中间位置记录的关键字与查找关键字比较,如果两者相等,则查找成功;否则利用中间位置记录将表分成前、后两个子表,如果中间位置记录的关键字大于查找关键字,则进一步查找前一子表,否则进一步查找后一子表。重复以上过程,直到找到满足条件的记录,使查找成功,或直到子表不存在为止,此时查找不成功。
posted on 2019-05-27 21:21 weirdo12138 阅读(81) 评论(1) 编辑 收藏 举报