Saturday, January 18, 2014

Move the Spaces to Front of the String

Problem: Given a string that has set of words and spaces, write a program to move the spaces to front of string, you need to traverse the array only once and need to adjust the string in place.
string = “move these spaces to beginning”
output =” movethesepacestobeginning”

Solution:
1) Maintain two indices i and j.
2) Traverse from end to beginning.
If the current index contains char, swap chars in index i with index j.
This will move all the spaces to beginning of the array.

#include<iostream>
using namespace std;
int main()
{
    char a[]="Move space to begining";
    int n=strlen(a)-1,count = n;
 
    //MoveSpace(a,0,strlen(a)-1);
    for(int i=n;i>=0;i--)
    {
        if(a[i] != ' ')
        a[count--] = a[i];
    }
     
    while(count>=0)
        a[count--] = ' ';
    cout << "After Space Moved to Begining" << a << endl;
 
    return 0;
}

Time Complexity: O(n) where n is the number of characters in input array.
Space Complexity: O(1).

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