2. matrix
#include <stdio.h>

struct term {
    int row;
    int col;
    int value;
};

void readSparse(struct term a[]) {
    int i, rows, cols, n;
    printf("Enter total rows and columns of matrix: ");
    scanf("%d%d", &rows, &cols);
    printf("Enter total non-zero elements: ");
    scanf("%d", &n);
    a[0].row = rows;
    a[0].col = cols;
    a[0].value = n;

    for(i = 1; i <= n; i++) {
        printf("Enter row, column and value for element %d: ", i);
        scanf("%d%d%d", &a[i].row, &a[i].col, &a[i].value);
    }
}

void displaySparse(struct term a[]) {
    int i, n = a[0].value;
    printf("\nRow\tCol\tValue\n");
    for(i = 0; i <= n; i++) {
        printf("%d\t%d\t%d\n", a[i].row, a[i].col, a[i].value);
    }
}

void simpleTranspose(struct term a[], struct term b[]) {
    int i, j, n = a[0].value;
    b[0].row = a[0].col;
    b[0].col = a[0].row;
    b[0].value = n;
    int currentb = 1;
    for(i = 0; i < a[0].col; i++) {
        for(j = 1; j <= n; j++) {
            if(a[j].col == i) {
                b[currentb].row = a[j].col;
                b[currentb].col = a[j].row;
                b[currentb].value = a[j].value;
                currentb++;
            }
        }
    }
}

void fastTranspose(struct term a[], struct term b[]) {
    int rowTerms[20], startingPos[20];
    int i, j, numCols = a[0].col, numTerms = a[0].value;
    b[0].row = numCols;
    b[0].col = a[0].row;
    b[0].value = numTerms;

    if(numTerms > 0) {
        for(i = 0; i < numCols; i++)
            rowTerms[i] = 0;
        for(i = 1; i <= numTerms; i++)
            rowTerms[a[i].col]++;

        startingPos[0] = 1;
        for(i = 1; i < numCols; i++)
            startingPos[i] = startingPos[i-1] + rowTerms[i-1];

        for(i = 1; i <= numTerms; i++) {
            j = startingPos[a[i].col]++;
            b[j].row = a[i].col;
            b[j].col = a[i].row;
            b[j].value = a[i].value;
        }
    }
}

int main() {
    struct term a[20], b[20];
    int choice;

    readSparse(a);
    printf("\nOriginal Sparse Matrix:");
    displaySparse(a);

    printf("\nChoose Operation:\n");
    printf("1. Simple Transpose\n");
    printf("2. Fast Transpose\n");
    printf("Enter your choice: ");
    scanf("%d", &choice);

    switch(choice) {
        case 1:
            simpleTranspose(a, b);
            printf("\nAfter Simple Transpose:");
            displaySparse(b);
            break;
        case 2:
            fastTranspose(a, b);
            printf("\nAfter Fast Transpose:");
            displaySparse(b);
            break;
        default:
            printf("Invalid choice!\n");
    }

    return 0;
}