实验5 数组和指针
实验5 数组和指针
1. 实验任务1
#include<stdio.h> #define N 5 void output(int x[], int n); int main() { int x[N]={9,55,30,27,22}; int i; int k; int t; printf("original array:\n"); output(x, N); k=0; for(i=1;i<N;++i) if(x[i]>x[k]) k=i; if(k!=N-1) { t = x[N-1]; x[N-1] = x[k]; x[k] = t; } printf("after swapped:\n"); output(x, N); return 0; } void output(int x[], int n) { int i; for(i=0; i<n; ++i) printf("%d ", x[i]); printf("\n"); }
#include <stdio.h> #define N 5 void output(int x[], int n); int main() { int x[N] = {9, 55, 30, 27, 22}; int i; int t; printf("original array:\n"); output(x, N); for(i=0; i<N-1; ++i) if(x[i] > x[i+1]) { t = x[i]; x[i] = x[i+1]; x[i+1] = t; } printf("after swapped:\n"); output(x, N); return 0; } void output(int x[], int n) { int i; for(i=0; i<n; ++i) printf("%d ", x[i]); printf("\n"); }
task1.c实现方式中,相较于原始数组,发生数据元素交换1次
算法是交换下标
task2.c实现方式中,相较于原始数组,发生数据元素交换3次
算法是交换元素
2. 实验任务2
#include <stdio.h> #define N 5 int binarySearch(int x[], int n, int item); int main() { int a[N] = {2, 7, 19, 45, 66}; 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 (x[mid]==item) return mid; else if (x[mid]>item) high = mid - 1; else low = mid + 1; } return -1; }
3.实验任务3
#include<stdio.h> #include<string.h> #define N 5 void selectsort(char str[][20],int n); int main(){ char name[][20]={"Bob","Bill","Joseph","Talor","George"}; int i; printf("输出初始名单:\n"); for(i=0;i<N;i++) printf("%s\n",name[i]); selectsort(name,N); printf("按字典输出名单:\n"); for(i=0;i<N;i++) printf("%s\n",name[i]); return 0; } void selectsort(char str[][20],int n){ int i,j,k,sign; char temp[20]; for(i=0;i<n-1;i++){ k=i; for(j=i+1;j<n;j++){ sign=strcmp(str[k],str[j]); if(sign>0) k=j; } if(k!=i){ strcpy(temp,str[i]); strcpy(str[i],str[k]); strcpy(str[k],temp); } } }
4.实验任务4
#include <stdio.h> int main() { int n; int *pn; n = 42; pn = &n; printf("&n = %#x, n = %d\n", &n, n); printf("&pn = %#x, pn = %#x\n", &pn, pn); printf("*pn = %d\n", *pn); return 0; }
(1)整型变量n的地址是0x62fe1c,存放的数是42
(2)指针变量pn的地址是0x62fe10,存放的是变量n的地址
(3)通过*pn间接访问的是变量n的值
5.实验任务5
#include <stdio.h> #define N 5 int main() { int a[N] = {1, 9, 2, 0, 7}; int i; int *p; for(i=0; i<N; ++i) printf("&a[%d] = %#x, a[%d] = %d\n", i, &a[i], i, a[i]); printf("\n"); for(i=0; i<N; ++i) printf("a+%d = %#x, *(a+%d) = %d\n", i, a+i, i, *(a+i)); printf("\n"); p = a; for(i=0; i<N; ++i) printf("p+%d = %#x, *(p+%d) = %d\n", i, p+i, i, *(p+i)); return 0; }
通过 a[i] 和 *(p+i) 都可以访问到数组元素a[i]
通过 &a[i] 和 p+i 都可以获得元素a[i]的地址