实验五

part1  二分法查找，

#include  <stdio.h>
const int N=5;
int binarySearch(int x[], int n, int item);
int main() {
    int a[N]={5,8,11,19,25};
    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;
}

#include  <stdio.h>
const int N=5;
int binarySearch(int *x, int n, int item);
int main() {
    int a[N]={9,10,23,45,71};
    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;
}

 

 

 

2. 用选择法排序对一组数据由小到大排序。

选出n个数中最小的数与第1个数交换；

选出次小的数与第2个交换；

以此类推，...; 选出次大的数与第n-1个数交换

#include <stdio.h>
#include <string.h>
void selectSort(char str[][20], int n ); 
int main() {
    char name[][20] = {"mary", "tom", "jojn", "cabdy", "gaccy"};
    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);
        }
    }
}

实验总结与体会

选择排序法和冒泡排序法是类似的，写完选择排序法之后也会对冒泡排序法有更深的理解与体会，

只是对于用指针来替换的方法还不是很熟练，容易写错指针变量，还要多用指针练习。

https://www.cnblogs.com/jiyuan201088/p/10932901.html

https://www.cnblogs.com/ls4computer/p/10931948.html

 https://www.cnblogs.com/couldi/p/10926335.html