1. 请编程实现二维数组的杨辉三角

#include <stdio.h>
#include <stdlib.h>
#include <string.h>int main()
{int n;scanf("%d", &n);int a[n][n];memset(a, 0, sizeof(a));a[0][0] = 1;for (int i = 1; i < n; i++){for (int j = 0; j < i + 1; j++){if (0 == j){a[i][j] = 1;}else{a[i][j] = a[i - 1][j - 1] + a[i - 1][j];}}}for (int i = 0; i < n; i++){for (int j = 0; j < i + 1; j++){printf("%4d", a[i][j]);}puts("");}
}

2. 请编程实现二维数组计算每一行和以及列和

#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]);}}printf("行和：");for (int i = 0; i < n; i++){int sum = 0;for (int j = 0; j < n; j++){sum += a[i][j];}printf("%4d", sum);}puts("");printf("列和：");for (int i = 0; i < n; i++){int sum = 0;for (int j = 0; j < n; j++){sum += a[j][i];}printf("%4d", sum);}puts("");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;
}