Thread: How to store a string letter by letter in a 2D matrix?

You had working code here.

Code:

void gridStr(char *line, char *key)
{    
    int columns = strlen(key)-1;
    int i = 0;
    while (line[i]) {
        putchar(line[i++]);
        if (i % columns == 0) putchar('\n');
    }
    if (i % columns != 0) putchar('\n');
}

What you lacked was a counter for rows.

Code:

void gridStr(char *line, char *key)
{    
    char mat[10][10];
    int columns = strlen(key)-1;
    int rows = 0;
    int i = 0;
    while (line[i]) {
        mat[rows][columns] = line[i++];  // store instead of print
        if (i % columns == 0) rows++
    }
    if (i % columns != 0) rows++;
}

Of course it doesn't print anything.
It's purpose is to compute the grid.

Here's something for you to study.

Code:

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

void trimNewline(char *line) {
    size_t len = strlen(line);
    if (len && line[len - 1] == '\n')
        line[len - 1] = '\0';
}

void inputLine(char *line, size_t max, const char *prompt) {
    printf("%s", prompt);
    if (fgets(line, max, stdin) == NULL) {
        fprintf(stderr, "No line read\n");
        exit(EXIT_FAILURE);
    }
    trimNewline(line);
}

void gridStr(char mat[10][10], size_t columns, const char *line)
{
    size_t r = 0, c = 0;
    int i = 0;
    while (line[i]) {
        mat[r][c] = line[i++];
        if ( ++c == columns ) {
            c = 0;
            r++;
        }
    }
}

void printGrid(const char mat[10][10], size_t rows, size_t columns) {
    for ( size_t r = 0 ; r < rows ; r++ ) {
        for ( size_t c = 0 ; c < columns ; c++ ) {
            putchar(mat[r][c]);
        }
        putchar('\n');
    }
}

int main(){
    char str[50];
    char key[50];

    inputLine(str, sizeof(str), "Please enter string:");
    inputLine(key, sizeof(key), "Please enter key:");

    size_t columns = strlen(key);
    size_t rows = (strlen(str) + columns - 1) / columns;
    char mat[10][10] = { { 0 } };

    gridStr(mat, columns, str);
    printGrid(mat, rows, columns);
     
    return 0;
}


$ gcc foo.c
$ ./a.out 
Please enter string:thislongline.
Please enter key:key
thi
slo
ngl
ine
.
$

First, anytime you start copy/pasting more than a few lines of code, you should be making a function out of it.


A note about line 50.
If the length of the line was a simple multiple of the length of the key, then a simple
rows = strlen(str) / columns would suffice.

But integer division rounds down, so if there are any excess characters to complete the last partial row, we need an extra row.