AI Coding & CSE Fundamentals

Palindrome String Check (No strrev)

#include <stdio.h>
#include <string.h>

int main() {
 char str[100];
 int i, len, flag = 1;

 printf("Enter a string: ");
 scanf("%s", str);

 len = strlen(str);

 for (i = 0; i < len/2; i++) {
 if (str[i] != str[len-i-1]) {
 flag = 0;
 break;
 }
 }

 if (flag) {
 printf("%s is a palindrome", str);
 } else {
 printf("%s is not a palindrome", str);
 }
 return 0;
}

Reverse a String

#include <stdio.h>
#include <string.h>

int main() {
 char str[100];
 int i, len;
 char temp;

 printf("Enter a string: ");
 scanf("%s", str);

 len = strlen(str);

 for (i = 0; i < len/2; i++) {
 temp = str[i];
 str[i] = str[len - i - 1];
 str[len - i - 1] = temp;
 }

 printf("Reversed string: %s\n", str);
 return 0;
}

Remove Vowels from a String

#include <stdio.h>
#include <string.h>
#include <stdbool.h>

bool isVowel(char c) {
    c = tolower(c);
    return (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
}

int main() {
    char str[100];
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);
    str[strcspn(str, "\n")] = 0;

    int j = 0;
    for (int i = 0; str[i] != '\0'; i++) {
        if (!isVowel(str[i])) {
            str[j++] = str[i];
        }
    }
    str[j] = '\0';

    printf("String after removing vowels: %s\n", str);
    return 0;
}

Remove Spaces from String

#include <stdio.h>
#include <string.h>

void removeSpaces(char *str) {
    int i, j = 0;
    for (i = 0; str[i] != '\0'; i++) {
        if (str[i] != ' ') {
            str[j++] = str[i];
        }
    }
    str[j] = '\0';
}

int main() {
    char str[] = " This is a string with spaces. ";
    removeSpaces(str);
    printf("%s", str);
    return 0;
}

Toggle Case of String Characters

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main() {
 char str[100];
 int i;

 printf("Enter a string: ");
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;

 for (i = 0; str[i] != '\0'; i++) {
 if (islower(str[i])) {
 str[i] = toupper(str[i]);
 } else if (isupper(str[i])) {
 str[i] = tolower(str[i]);
 }
 }

 printf("Toggled string: %s\n", str);
 return 0;
}

Count Vowels, Consonants, Digits, and Spaces in a String

#include <stdio.h>
#include <string.h>

int main() {
  char str[100];
  int vowels = 0, consonants = 0, digits = 0, spaces = 0;
  printf("Enter a string: ");
  fgets(str, sizeof(str), stdin);

  for (int i = 0; str[i] != '\0'; i++) {
    char ch = str[i];
    if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
      ch = (ch >= 'A' && ch <= 'Z') ? (ch + 32) : ch;
      if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
        vowels++;
      } else {
        consonants++;
      }
    } else if (ch >= '0' && ch <= '9') {
      digits++;
    } else if (ch == ' ') {
      spaces++;
    }
  }

  printf("Vowels: %d\n", vowels);
  printf("Consonants: %d\n", consonants);
  printf("Digits: %d\n", digits);
  printf("Spaces: %d\n", spaces);
  return 0;
}

String Case Conversion

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main() {
 char str[100];
 int i;

 printf("Enter a string: ");
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;

 for (i = 0; str[i] != '\0'; i++) {
 if (islower(str[i])) {
 str[i] = toupper(str[i]);
 } else if (isupper(str[i])) {
 str[i] = tolower(str[i]);
 }
 }

 printf("Modified string: %s\n", str);
 return 0;
}

Compare Two Strings (Without strcmp)

#include <stdio.h>

int main() {
 char str1[100], str2[100];
 int i = 0, flag = 0;

 scanf("%s", str1);
 scanf("%s", str2);

 while (str1[i] != '\0' || str2[i] != '\0') {
 if (str1[i] != str2[i]) {
 flag = 1;
 break;
 }
 i++;
 }

 if (flag == 0 && str1[i] == '\0' && str2[i] == '\0')
 printf("Strings are equal");
 else
 printf("Strings are not equal");

 return 0;
}

String Concatenation (Without strcat)

#include <stdio.h>
#include <string.h>

int main() {
 char str1[100] = "Hello, ";
 char str2[] = "World!";
 int i, j;

 for (i = 0; str1[i] != '\0'; i++);

 for (j = 0; str2[j] != '\0'; j++) {
 str1[i] = str2[j];
 i++;
 }
 str1[i] = '\0';

 printf("%s\n", str1);
 return 0;
}

Copying Strings

#include <stdio.h>

int main() {
 char source[] = "Hello!";
 char destination[10];
 int i = 0;

 while (source[i] != '\0') {
 destination[i] = source[i];
 i++;
 }
 destination[i] = '\0';

 printf("Copied string: %s\n", destination);
 return 0;
}

🔥Solve LeetCode Problems Daily 👉https://t.me/+9BYfwzAg1dQzODQ1

String Length (No strlen)

#include <stdio.h>

int main() {
 char str[] = "Hello";
 int length = 0;
 while (str[length] != '\0') {
 length++;
 }
 printf("Length: %d\n", length);
 return 0;
}

Input and Print a String

#include <stdio.h>
#include <string.h>

int main() {
 char str[100];
 printf("Enter a string: ");
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;
 printf("You entered: %s\n", str);
 return 0;
}

Spiral Matrix Traversal

#include <stdio.h>

int main() {
    int rows, cols, i, j;
    scanf("%d %d", &rows, &cols);
    int matrix[rows][cols];
    for (i = 0; i < rows; i++) {
        for (j = 0; j < cols; j++) {
            scanf("%d", &matrix[i][j]);
        }
    }
    int top = 0, bottom = rows - 1, left = 0, right = cols - 1, dir = 0;
    while (top <= bottom && left <= right) {
        if (dir == 0) {
            for (i = left; i <= right; i++) {
                printf("%d ", matrix[top][i]);
            }
            top++;
        } else if (dir == 1) {
            for (i = top; i <= bottom; i++) {
                printf("%d ", matrix[i][right]);
            }
            right--;
        } else if (dir == 2) {
            for (i = right; i >= left; i--) {
                printf("%d ", matrix[bottom][i]);
            }
            bottom--;
        } else if (dir == 3) {
            for (i = bottom; i >= top; i--) {
                printf("%d ", matrix[i][left]);
            }
            left++;
        }
        dir = (dir + 1) % 4;
    }
    printf("\n");
    return 0;
}

Print Boundary Elements of a Matrix

#include <stdio.h>

int main() {
    int rows, cols, i, j;
    printf("Enter the number of rows: ");
    scanf("%d", &rows);
    printf("Enter the number of columns: ");
    scanf("%d", &cols);

    int matrix[rows][cols];

    printf("Enter the elements of the matrix:\n");
    for (i = 0; i < rows; i++)
        for (j = 0; j < cols; j++)
            scanf("%d", &matrix[i][j]);

    printf("Boundary elements are:\n");
    for (i = 0; i < rows; i++) {
        for (j = 0; j < cols; j++) {
            if (i == 0 || i == rows - 1 || j == 0 || j == cols - 1)
                printf("%d ", matrix[i][j]);
            else
                printf("  ");
        }
        printf("\n");
    }

    return 0;
}

Print Lower Triangle of a Matrix

#include <stdio.h>

int main() {
  int matrix[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
  int rows = 3;
  int cols = 3;

  for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
      if (j <= i) {
        printf("%d ", matrix[i][j]);
      } else {
        printf("  ");
      }
    }
    printf("\n");
  }

  return 0;
}

Print Upper Triangle of a Matrix

#include <stdio.h>

int main() {
  int rows, cols, matrix[10][10], i, j;

  printf("Enter the number of rows: ");
  scanf("%d", &rows);
  printf("Enter the number of columns: ");
  scanf("%d", &cols);

  printf("Enter the elements of the matrix:\n");
  for (i = 0; i < rows; i++) {
    for (j = 0; j < cols; j++) {
      scanf("%d", &matrix[i][j]);
    }
  }

  printf("Upper triangle of the matrix:\n");
  for (i = 0; i < rows; i++) {
    for (j = 0; j < cols; j++) {
      if (j >= i) {
        printf("%d ", matrix[i][j]);
      } else {
        printf("  ");
      }
    }
    printf("\n");
  }

  return 0;
}

Diagonal Sum of a Square Matrix

#include <stdio.h>

int main() {
 int matrix[10][10];
 int rows, cols, i, j, sum = 0;

 printf("Enter the number of rows (and columns): ");
 scanf("%d", &rows);
 cols = rows;

 printf("Enter the elements of the matrix:\n");
 for (i = 0; i < rows; i++) {
 for (j = 0; j < cols; j++) {
 scanf("%d", &matrix[i][j]);
 }
 }

 for (i = 0; i < rows; i++) {
 sum += matrix[i][i];
 }

 printf("Diagonal sum: %d\n", sum);

 return 0;
}