Given an array [a1b2c3d4] convert to [abcd1234] with 0(1) space and O(n) time

http://learn.hackerearth.com/forum/134/there-is-a-string-like-abcde12345-convert-it-in-form-of/

从 a1b2c3d4 --> abcd1234

voidconvertArray(char* array, intlength) {

inti;

if(length >=4) {

convertArray(array, length/2);

convertArray(array + length/2, length/2);

for(i=0; i<length/4; i++) {

swap(array+(length/2)/2+i, array+(length/2)+i);

} 

}

}
 

从abcd1234 --> a1b2c3d4 是上面过程的反过程

void fun(char s[], int n)    {        //  Base case        if(n == 2)            return;        else        {            swap_str(s+n/4, s+n/2, n/4);            fun(s, n/2);            fun(s + n/2, n/2);        }    }void swap_str(char s1[], char s2[], int n){    for(int i = 0; i < n; i++)        swap(s1[i], s2[i]);}