Array Input off by one index in C. Caesar Block Shift - c

Question

Here I have code that inputs from stdin a stream of characters into an array. It then converts that array to a 2d array. Then it changes that array from row column order to column row order. Then it prints out the new array creating a Caesar shift encryption. The issue I am having is that my array is starting to input characters into the array with the second user typed character and I am not sure why.
For Example, if I type "Hello" into the console, only "ello" is put into the array.
Any thoughts? Thanks!
//
// main.c
// Caesar Block Cypher
//
// Created by Jacob Byerline on 10/20/18.
// Copyright © 2018 Jacob Byerline. All rights reserved.
//
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
int main(void){
//The size is extended by the input with the value of the provisional
char *str;
int inputChar;
int i, j;
size_t size = 0;
size_t len = 0;
printf("input string : ");
inputChar = getchar();
str = realloc(NULL, sizeof(char)*size);//size is start size
if(!str)return *str;
while(EOF!=(inputChar=fgetc(stdin)) && inputChar != '\n'){
if(isalpha(inputChar)){
str[len++]=inputChar;
if(len==size){
str = realloc(str, sizeof(char)*(size+=16));
if(!str)return *str;
}
}
}
str[len++]='\0';
int squareOfLen = sqrt(len);
int twoDimensionalArraySize = squareOfLen + 1;
//printf("%lu \n", len);
//printf("%d \n", squareOfLen);
//printf("%d \n", twoDimensionalArraySize);
char twoDstr[twoDimensionalArraySize][twoDimensionalArraySize];
char FINALtwoDstr[twoDimensionalArraySize][twoDimensionalArraySize];
memcpy(twoDstr, str, twoDimensionalArraySize * 2 * sizeof(int));
for(i=0; i<twoDimensionalArraySize; i++){
for(j=0; j<twoDimensionalArraySize; j++){
printf("2D Array[%d][%d] = %c\n",i,j,twoDstr[i][j]);
}
}
for(i=0; i<twoDimensionalArraySize; i++){
for(j=0; j<twoDimensionalArraySize; j++){
FINALtwoDstr[i][j] = twoDstr[j][i];
//printf("2D Array[%d][%d] = %c\n",i,j,FINALtwoDstr[i][j]);
printf("%c",FINALtwoDstr[i][j]);
}
}
printf("\n");
return 0;
}

Answer 1

Remove
inputChar = getchar();
This is taking up 'H' from your input stream.
See here https://ideone.com/ZwT9Iq
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
int main(void){
//The size is extended by the input with the value of the provisional
char *str;
int inputChar;
int i, j;
size_t size = 0;
size_t len = 0;
printf("input string : ");
//inputChar = getchar();
str = realloc(NULL, sizeof(char)*size);//size is start size
if(!str)return *str;
while(EOF!=(inputChar=fgetc(stdin)) && inputChar != '\n'){
if(isalpha(inputChar)){
str[len++]=inputChar;
if(len==size){
str = realloc(str, sizeof(char)*(size+=16));
if(!str)return *str;
}
printf("%c", inputChar);
}
}
printf("\n");
str[len]='\0';
int squareOfLen = sqrt(len);
int twoDimensionalArraySize = squareOfLen + 1;
//printf("%lu \n", len);
//printf("%d \n", squareOfLen);
//printf("%d \n", twoDimensionalArraySize);
char twoDstr[twoDimensionalArraySize][twoDimensionalArraySize];
char FINALtwoDstr[twoDimensionalArraySize][twoDimensionalArraySize];
memcpy(twoDstr, str, twoDimensionalArraySize * 2 * sizeof(int));
for(i=0; i<twoDimensionalArraySize; i++){
for(j=0; j<twoDimensionalArraySize; j++){
printf("2D Array[%d][%d] = %c\n",i,j,twoDstr[i][j]);
}
}
for(i=0; i<twoDimensionalArraySize; i++){
for(j=0; j<twoDimensionalArraySize; j++){
FINALtwoDstr[i][j] = twoDstr[j][i];
//printf("2D Array[%d][%d] = %c\n",i,j,FINALtwoDstr[i][j]);
printf("%c",FINALtwoDstr[i][j]);
}
}
printf("\n");
return 0;
}
output
Hleol

Answer 2

Ignoring allocation and check for alpha-ness, you do this:
inputChar = getchar(); // Read first char
while (EOF != (inputChar=fgetc(stdin)) // read further chars
&& inputChar != '\n') {
str[len++]=inputChar;
}
That means that the first character is consumed, but never stored. Instead, you could do this:
inputChar = getchar(); // Read first char
while (inputChar != EOF && inputChar != '\n') {
str[len++]=inputChar;
inputChar=fgetc(stdin) // read further chars
}
But there are other issues with your code:
You start with an allocation of zero bytes, because size is 0;
You should allocate before you store, otherwise you write beyond the end of the buffer;
When you add the null terminator, you probably shouldn't increase len, because the '\0' isn't part of the locical length of the string, even if you have to allocate space for it, which you don't in all cases;
The square of len is len * len, not sqrt(len): That's the square root;
You square the dimension twice: If len is 3, you want an 3×3 array, but you try to allocate a 9×9 array on the stack;
You can't copy len*len * 2 * sizeof(int) bytes from str, which has only len bytes.
There's probably more in the last part; I haven't looked too closely.