1.请编程实现二维数组的杨慧三角

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <unistd.h>
int main(int argc, const char *argv[])
{int n;printf("please enter n:");scanf("%d",&n);int arr[n][n];for(int i=0;i<n;i++){for(int j=0;j<=i;j++){if(j==0 || j==i){arr[i][j]=1;}else{arr[i][j]=arr[i-1][j]+arr[i-1][j-1];}printf("%d\t",arr[i][j]);}puts("");}return 0;
}

⒉请编程实现二维数组计算每一行的和以及列和

int main(int argc, const char *argv[])
{int n,m;printf("please enter n and m:");scanf("%d %d",&n,&m);int arr[n][m];printf("please enter arr:");for(int i=0;i<n;i++){for(int j=0;j<m;j++){scanf("%d",&arr[i][j]);}}for(int i=0;i<n;i++){for(int j=0;j<m;j++){printf("%d ",arr[i][j]);}puts("");}//计算每一行的和int sum1;for (int i=0;i<n;i++) {sum1=0;for (int j=0;j<m;j++) {sum1+=arr[i][j];}printf("第%d行的和为%d\n",i+1,sum1);}//计算每一列的和int sum2;for (int j=0;j<m;j++) {sum2=0;for (int i=0;i<n;i++) {sum2+=arr[i][j];}printf("第%d列的和为%d\n",j+1,sum2);}return 0;
}

3.请编程实现二维数组计算第二大值

#include <stdio.h>
#include <stdlib.h>
#include <string.h>int main()
{int n;scanf("%d", &n);int a[n][n];for (int i = 0; i < n; i++){for (int j = 0; j < n; j++){scanf("%d", &a[i][j]);}}int max = 0;for (int i = 0; i < n; i++){for (int j = 0; j < n; j++){if (max < a[i][j]){max = a[i][j];}}}int sec_max = 0;for (int i = 0; i < n; i++){for (int j = 0; j < n; j++){if (sec_max < a[i][j] && max > a[i][j]){sec_max = a[i][j];}}}printf("第二大：%d\n", sec_max);return 0;
}

4.请使用非函数方法实现系统函数strcat,strcmp,strcpy,strlen

#include <stdio.h>
#include <stdlib.h>
#include <string.h>void my_strcmp(char s1[], char s2[])
{int i = 0;while (s1[i] == s2[i]){if (s1[i] == '\0' || s2[i] == '\0'){break;}i++;}if (s1[i] > s2[i]){puts("s1 > s2");}else if (s1[i] < s2[i]){puts("s1 < s2");}else{puts("s1 == s2");}
}void my_strcpy(char s1[], char s2[])
{int i = 0;while (s2[i] != '\0'){s1[i] = s2[i];i++;}s1[i] = '\0';
}int my_strlen(char s[])
{int i;for (i = 0; s[i] != '\0'; i++);return i;
}void my_strcat(char s1[], char s2[])
{int i = 0;while (s1[i] != '\0'){i++;}int j = 0;while (s2[j] != '\0'){s1[i + j] = s2[j];j++;}s1[i + j] = '\0';
}int main()
{char s1[20] = "hello";char s2[20] = "world";my_strcmp(s1, s2);printf("%s len: %d\n", s1, my_strlen(s1));my_strcpy(s1, s2);printf("%s\n", s1);my_strcat(s1, s2);printf("%s\n", s1);return 0;
}