Multiple Choice Questions

(1) Given declarations int i; char x[10];, the correct statement to assign values to array x is:

for(i=0; i<6; i++) x[i]=getchar();

(2) For character arrays delcared as char a[]="abcd"; char b[]={'a','b','c','d','e'};:

Both arrays have identical length due to null terminator inclution.

(3) With declaration int i; int x[3][3]={2,3,4,5,6,7,8,9,10};, executing:

for(i=0;i<3;i++) printf("%4d",x[i][2-i]);

Outputs: 4 6 8

(4) Valid two-dimensional array initialization:

int a[][3] = {1,2,3,4,5,6};

(5) Correct array characteristic:

Elements are distinguished through subscript indexing.

(6) To output the lexicographically larger string between str1 and str2:

if(strcmp(str1,str2)>0) printf("%s",str1); else printf("%s",str2);

(7) For array aa[4][4] = {{1,2,3,4},{5,6,7,8},{3,9,10,2},{4,2,9,6}}:

int i, s = 0;
for (i = 0; i < 4; i++)
   s += aa[i][1];
printf("%d\n", s);

Result: 19

(8) Character array str[15] = "hello!" has actual character count:

printf("%d\n", strlen(str)); // Output: 6

(9) After input "happy!":

char str[14] = {"I am "};
strcat(str, "sad!");
scanf("%s", str);
printf("%s", str); // Output: happy!

(10) Incorrect array description:

Remaining elements initialize to zero, not to last specified value.

Fill-in-the-Blank Questions

(1) For int i=3,x[4]={1,2,3};, element x[i] equals 0.

(2) String "I am a student" has length 14, with a[3] containing 'm'.

(3) In int k[3][4]={{1,2,3,4},{5,6,7,8},{9,10,11,12}}: k[2][1] is 10, k[1][2] is 7.

(4) Array a[4][4] has row lower bound 0 and column upper bound 3.

(5) For char a[]="abcdef":

printf("%d,%d\n",sizeof(a),strlen(a)); // Output: 7,6

(6) Program execution result:

char str[20] = "This is my book";
str[4] = '\0';
str[9] = '\0';
printf(" %d", strlen(str)); // Output: 4

(7) String comparison program outputs:

char name[3][20] = { "Tony", "Join", "Mary" };
int m = 0, k;
for (k = 1; k <= 2; k++)
     if (strcmp(name[k], name[m]) > 0)
         m = k;
puts(name[m]); // Output: Tony

(8) Statistical computation with input 20 30 5 85 40 produces:

max=85
min=5
sum=180
aver=30.00

(9) Charactre extraction program with input This_is_a_C_Program! generates:

Ti_saCPorm
Tss_Pgm

(10) Character counting program yields:

char s[] = "12345678";
int c[4] = { 0 }, k, i;
for (k = 0; s[k]; k++) {
    switch (s[k]) {
        case'1': i = 0; break;
        case'2': i = 1; break;
        case'3': i = 2; break;
        case'4': i = 3;
    }
    c[i]++;
}
// Output: 1 1 1 5

Programming Exercises

(1) Find minimum value and position among 15 integers:

#include<stdio.h>
int main() {
    int data[15], pos = 0;
    
    for (int idx = 0; idx < 15; idx++)
        scanf("%d", &data[idx]);
        
    for (int idx = 1; idx < 15; idx++)
        if (data[idx] < data[pos])
            pos = idx;
            
    printf("Minimum: %d at position: %d", data[pos], pos);
    return 0;
}

(2) Convert decimal to hexadecimal representation:

#include<stdio.h>
int main() {
    int num, digits[16], count = 0;
    
    do {
        scanf("%d", &num);
        if (num < 0) printf("Enter positive integer:\n");
    } while(num < 0);
    
    while(num) {
        digits[count] = num % 16;
        num /= 16;
        count++;
    }
    
    for (int idx = count-1; idx >= 0; idx--) {
        if (digits[idx] < 10) 
            printf("%d", digits[idx]);
        else 
            printf("%c", 'A' + digits[idx] - 10);
    }
    return 0;
}

(3) Count comma-separated words in string:

#include<stdio.h>
int main() {
    char text[100];
    int words = 0, active = 0;
    
    gets(text);
    for (int idx = 0; text[idx] != '\0'; idx++) {
        if (text[idx] == ',') 
            active = 0;
        else if (!active) {
            active = 1;
            words++;
        }
    }
    printf("Words: %d\n", words);
    return 0;
}

(4) Sort even-indexed characters in ascending order:

#include<stdio.h>
#include<string.h>
int main() {
    char input[100];
    int marker;
    
    gets(input);
    
    for (int base = 0; base < strlen(input)-2; base += 2) {
        marker = base;
        for (int compare = base+2; compare < strlen(input); compare += 2)
            if (input[compare] < input[marker]) 
                marker = compare;
                
        if (marker != base) {
            input[marker] ^= input[base];
            input[base] ^= input[marker];
            input[marker] ^= input[base];
        }
    }
    puts(input);
    return 0;
}

(5) Generate Pascal's triangle for 10 rows:

#include<stdio.h>
int main() {
    int triangle[10][10];
    
    for (int row = 0; row < 10; row++) {
        triangle[row][0] = triangle[row][row] = 1;
    }
    
    for (int row = 2; row < 10; row++)
        for (int col = 1; col < row; col++)
            triangle[row][col] = triangle[row-1][col-1] + triangle[row-1][col];
            
    for (int row = 0; row < 10; row++) {
        for (int col = 0; col <= row; col++)
            printf("%4d", triangle[row][col]);
        printf("\n");
    }
    return 0;
}

(6) Concatenate string with its reverse:

#include<stdio.h>
#include<string.h>
int main() {
    char source[100], target[100];
    int length;
    
    scanf("%s", source);
    length = strlen(source);
    
    for (int idx = 0; idx < length; idx++)
        target[idx] = source[idx];
        
    for (int idx = 0; idx < length; idx++)
        target[length + idx] = source[length - 1 - idx];
        
    target[2 * length] = '\0';
    printf("%s\n", target);
    return 0;
}

(7) Encrypt four-digit number using substitution cipher:

#include<stdio.h>
int main() {
    int number, result = 0, digits[4];
    scanf("%d", &number);
    
    for (int pos = 3; pos >= 0; pos--) {
        int adjusted_pos = abs(pos - 3);
        digits[adjusted_pos] = (number % 10 + 5) % 10;
        result = result * 10 + digits[adjusted_pos];
        number /= 10;
    }
    printf("Encrypted: %d", result);
    return 0;
}

(8) Locate first occurrence of value 18 in matrix:

#include<stdio.h>
int main() {
    int matrix[3][4] = {{3,4,5,18}, {8,12,16,54}, {43,34,18,7}};
    int row, col;
    
    for (row = 0; row < 3; row++) {
        for (col = 0; col < 4; col++)
            if (matrix[row][col] == 18) break;
        if (col < 4) break;
    }
    printf("Value 18 found at row %d, column %d\n", row+1, col+1);
    return 0;
}

(9) Analyze 4x4 array with formula a[i][j]=3i+2j-6:

#include<stdio.h>
int main() {
    int grid[4][4], row_sum = 0;
    float col_avg = 0;
    int negative_count = 0;
    
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < 4; j++)
            grid[i][j] = 3 * i + 2 * j - 6;
            
    for (int j = 0; j < 4; j++)
        row_sum += grid[1][j];
        
    for (int i = 0; i < 4; i++)
        col_avg += grid[i][3];
    col_avg /= 4;
    
    for (int i = 0; i < 4; i++)
        if (grid[i][i] < 0)
            negative_count++;
            
    printf("Row 2 sum: %d\n", row_sum);
    printf("Column 4 average: %f\n", col_avg);
    printf("Negative diagonal elements: %d\n", negative_count);
    return 0;
}

(10) Josephus problem implementation:

#include<stdio.h>
int main() {
    int passwords[100];
    int people, limit, current = 0;
    
    printf("Enter people count and initial limit: ");
    scanf("%d%d", &people, &limit);
    printf("Enter %d passwords: ", people);
    
    for (int i = 0; i < people; i++)
        scanf("%d", &passwords[i]);
        
    printf("\nElimination order: ");
    
    for (int eliminated = 0; eliminated < people; eliminated++) {
        int counter = 1;
        while (counter < limit) {
            while (passwords[current] == 0)
                current = (current + 1) % people;
            counter++;
            current = (current + 1) % people;
        }
        
        while (passwords[current] == 0)
            current = (current + 1) % people;
            
        printf("%d ", current + 1);
        limit = passwords[current];
        passwords[current] = 0;
    }
    return 0;
}