How to modify string to char array in C/C++? - c++

Question

i'm writing a program called 'Zuma'. The program works like this.
Input:
ACCBA // a string make up of char from 'A' to 'Z'
5 // number of inputs
1 B // insert char 'B' to position '1' of the string
0 A // and so on...
2 B
4 C
0 A
When 3 same chars next to each other, we erase/remove/delete them from the string.
For example, when we insert char 'C' to position 2 of string 'ABCC', we got 'AB' because
'CCC' are removed from the string.
Output:
ABCCBA
AABCCBA
AABBCCBA // the process is AABBCCCBA -> AABBBA -> AAA -> -
- // if the string is empty, we output "-"
A
This is my code with string:
#include <iostream>
using namespace std;
int main()
{
int n, pos;
int k = 0;
int length = 0;
string zuma, marble; // i use string
cin >> zuma;
cin >> n;
for (int i = 0; i < n; ++i)
{
cin >> pos >> marble;
zuma.insert(pos, marble);
length = zuma.length(); // length of current string
// compare each char from pos[i] with pos[i+1] and pos[i+2]
// and then ++i until end of string
while (k != length && length >= 3)
{
if (zuma[k] == zuma[k + 1] && zuma[k] == zuma[k + 2])
{
zuma.erase(k, 3); // erase 3 same char in the string
k = 0; // set k to zero to start from pos[0] again
}
else
k++;
}
// if string is not empty
if (!zuma.empty())
{
cout << zuma << endl; // output the current char in the string
k = 0;
}
else
cout << "-" << endl;
}
return 0;
}
This is my code with char array:
#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
void append (char subject[], const char insert[], int pos) {
char buf[100] = {};
strncpy(buf, subject, pos);
int len = strlen(buf);
strcpy(buf+len, insert);
len += strlen(insert);
strcpy(buf+len, subject+pos);
strcpy(subject, buf);
}
int main()
{
int n, pos;
int k = 0;
int length = 0;
char zuma[100], marble[100];
scanf("%s", zuma);
scanf("%d", &n);
for (int i = 0; i < n; ++i)
{
scanf("%d %s", &pos, marble);
append(zuma, marble, pos); // acts like string::insert
length = strlen(zuma);
while (k != length && length >= 3)
{
if (zuma[k] == zuma[k + 1] && zuma[k] == zuma[k + 2])
{
//zuma.erase(k, 3); // need help with this part to remove 3 same chars like string::erase
k = 0;
}
else
k++;
}
if (strlen(zuma) != 0)
{
printf("%s\n", zuma);
k = 0;
}
else
printf("%s\n","-");
}
return 0;
}
My problem is how to write a function to remove 3 same chars just like what string::erase do?
Thanks for your help!!

Answer 1

You can use memmove to copy the remainder of the string to the position of the characters to remove. Use strlen to determine how much bytes to move. Note you cannot use strcpy because the source and destination buffers overlap.
if (zuma[k] == zuma[k + 1] && zuma[k] == zuma[k + 2])
{
int len = strlen(zuma+k+3) + 1; // +1 to copy '\0' too
memmove(zuma+k, zuma+k+3, len);
k = 0;
}