C++ Can't Figure Out How To Shuffle Image -

i've been stuck on bit now. need break image down 9 boxes(2d array) , shuffle it. imported image twice, once src , once target, 2 arrays. need src image shuffle , output target, without repeating tile, cant figure out how that....here's code:

#include "pgmio.h" #include <iostream> #include <ctime>  void shuffle_image_3(pgm src, pgm & target);  int main(int argc, char ** argv) {     srand(time(null));      pgm src, target;     readpgm("random.pgm", src); //2d array src     readpgm("random.pgm", target); //2d array target      shuffle_image_3(src, target);     writepgm("random_shuffled.pgm", target);     system("random_shuffled.pgm");     return 0; }  void shuffle_image_3(pgm src, pgm & target) {     if (src.row != target.row || src.col != target.col) {         return;     } //if sizes aren't equal, returns nothing      //"used[i][j]==true means tile in source     //at row , column j has been copied target     //initially, false, meaning none of     //tiles in source have been copied      bool used[3][3];     (int = 0; < 3; i++) {         (int j = 0; j < 3; j++) {             used[i][j] == false;         }     }     (int = 0; < 3; i++) {         (int j = 0; j < 3; j++) {             //randomly select tile in src             //copy pixel values tile target             int r, c;             {                 //randomly select tile in src                 r = rand() % 3;                 c = rand() % 3;             } while (used[r][c] == true);              used[r][c] == true;             //dont know how move tile @ row r , col c src            //to target @ row , col j          }     } }