Unable to replace blank spaces in the string correctly

Question

I don't know why it is giving the wrong output(appending all remaining numbers in the string at last)can any pls help me out!!

#include <iostream>
#include <bits/stdc++.h>
using namespace std;    
int main()
{string str="08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00\
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65\
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91\
22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80\
24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50\
32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70\
67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21\
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72\
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95\
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92\
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57\
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58\
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40\
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66\
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69\
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36\
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16\
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54\
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48";
int cnt=0;
for(int i=0;str[i];i++)
 {
 if(str[i]!=' ')
   {
     str[cnt++]=str[i];
   }
 }     
str[cnt] = '\0';
cout<<str<<endl;
} 

This is how it is displaying as output

Thank you

Answer 1

Not sure why you're trying to change str variable in place. Why don't you use a temporary string variable to do that?

Try this:

#include <iostream>
#include <bits/stdc++.h>

using namespace std;    

int main() {
    string str="08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 \
                49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00\
                81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65\
                52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91\
                22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80\
                24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50\
                32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70\
                67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21\
                24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72\
                21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95\
                78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92\
                16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57\
                86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58\
                19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40\
                04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66\
                88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69\
                04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36\
                20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16\
                20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54\
                01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48";
    
    string tmp = "";
    
    for(char& c : str) if(c != ' ') tmp += c;
    str = tmp;
    
    cout << str << endl;
}

Answer 2

Strings can be split (with any whitespace in between) "like this" -> "like" " " "this".

I.e. (guessing a little a the desired outcome):

string str=
"08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 "
"49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00 "
"81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65 "
"52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91 "
"22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80 "
"24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50 "
"32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70 "
"67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21 "
"24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72 "
"21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95 "
"78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92 "
"16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57 "
"86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58 "
"19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40 "
"04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66 "
"88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69 "
"04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36 "
"20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16 "
"20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54 "
"01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48 ";

No need for the line continuation here \<newline>, more of an obstacle.

Concerning the unexpected output of the rest of the string at the end:
Overwriting a letter with the '\0' does not have the terminating effect in a c++-string as it has in most character sequence handling functions in C.

As Botje mentions in the comments:

You overwrite 2/3 of the string, but what do you do with the remaining 1/3? You should truncate the string by either taking a substring or calling resize.

I.e. that is the way to change the effective length of a C++ string.