sorting an 2d array by keeping track of index and get the first 9 values.

Using Arduino Programming Questions
1

I have this code that :
1)reads all 16 analog inputs of an arduino Mega.
2) Then it puts the values in an 2d array ( the seccond row is then so i can keep a track of the index).

Then try to sort the array and get the 9 maximum values sorted in an other 2d array MaxValues[][] by keeping the index. It doesn't . all it does is filling all 9 spaces with the bigest value and the index of it.

this is the code that I am using :

int gauge[2][16] = {
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
};

int MaxValues[2][9] = {
  {0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 1, 2, 3, 4, 5, 6, 7, 8}
};

int f = 0; //flag value 1
int flag = 0; // flag value 2
void setup()
{
  Serial.begin(9600);
}

void loop() {
  for (int i = 0; i <= 15; i++) {  // begin and read all 16 analog and place then in the first row of gauge[][] aray
    gauge[0][i] = analogRead(i);
  }
  //  for (int j = 0; j <= 15; j++) {
  //    Serial.print(gauge[0][j]);
  //    if (j < 15) {
  //      Serial.print(",");
  //    } else {
  //      Serial.println(",");
  //    }
  //    delay(10);
  //  }
  for (int k = 0; k <= 15; k++) {
    for (int l = 0; l <= 15; l++) {
      f = 15;
      for (int x = 0; x <=8; x++) {      
        if (gauge[0][l] > MaxValues[0][x]) {  // if the value is biger than MaxValue[][] you have to start moving all values one place next and then place the value that was biger at the opened space in MaxValues[][] array
          if ( f == 15 ) {
            flag = 15;
          }
          for (int m = 8; m > x; m--) {
            if (flag == 15) {
              MaxValues[0][m] = MaxValues[0][m - 1];
              MaxValues[1][m] = MaxValues[1][m - 1];
              MaxValues[0][x] = gauge[0][l];
              MaxValues[1][x] = gauge[1][l];
              flag = 0;
              f = 0;
            }
          }
        }
      }
    }
  }

  for (int row = 0; row <=1; row++)
  {
    for (int col = 0; col <=8 ; col++)
    {
      Serial.print(MaxValues[row][col]);
      Serial.print("\t");
    }
    Serial.println();
  }

}

All i am tryng to do is keep track and sorted witch 9 sensors out of my 16 had the biggest values.

any ideas are more than welcome.

2

Just do a straight 'bubble-sort'

  // if you don't want to sort in place fill anew array with values and index first
  for (uint8_t c = 0; c < NR_ENTRIES - 1; c++) { // do a bubble sort
    for (uint8_t d = 0; d < NR_ENTRIES - c - 1; d++) {
      if (gauge[0][d] > gauge[0][d + 1]) { // compare
        for (uint8_t e = 0; e < 2; e++) {  // swap both values & index
          int tempval = gauge[e][d];
          gauge[e][d] = gauge[e][d + 1];
          gauge[e][d + 1] = tempval;
        }
      }
    }
  }
  // after this fill the other array with the 9 values you want
3

the first nine will be the biggest and the index will be there ?

4 
if (gauge[0][d] > gauge[0][d + 1])

actually this sorts low to high for high to low use

if (gauge[0][d] < gauge[0][d + 1])

and yes

for (uint8_t e = 0; e < 2; e++) {  // swap both values & index

both values are swapped, that includes the index. Important is of course not just to copy code like this, but to make sure you understand it.
Bubble_sort

5

it works perfect ! but the code needs a small change to the part of the analoge read.

for (int i = 0; i <= 15; i++) {  // begin and read all 16 analog and place then in the first row of gauge[][] aray
    midle = analogRead(i);
    midle = midle + analogRead(i);
    midle = midle + analogRead(i);
    gauge[0][i] = midle / 3;
    gauge[1][i] = i;
  }

before it couldn't keep the index, it was suffling the index.

now with :

gauge[1][i] = i;

we create the index from the beggining in every cycle.

and of course i read three times and get the midle of the sum for more stable readings in the analogRead()

Any way ! it is solved ! who ever needs to to the same : the entire code is :

int gauge[2][16] = {
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
};

int MaxValues[2][9] = {
  {0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 1, 2, 3, 4, 5, 6, 7, 8}
};
//int tempval[2][1];
int midle;
int f = 0; //flag value 1
int flag = 0; // flag value 2
void setup()
{
  Serial.begin(9600);
}

void loop() {
  for (int i = 0; i <= 15; i++) {  // begin and read all 16 analog and place then in the first row of gauge[][] aray
    midle = analogRead(i);
    midle = midle + analogRead(i);
    midle = midle + analogRead(i);
    gauge[0][i] = midle / 3;
    gauge[1][i] = i;
  }
  for (uint8_t c = 0; c < 15 - 1; c++) { // do a bubble sort
    for (uint8_t d = 0; d < 15 - c - 1; d++) {
      if (gauge[0][d] > gauge[0][d + 1]) { // compare
        for (uint8_t e = 0; e <= 1; e++) { // swap both values & index
          int tempval = gauge[e][d];
          gauge[e][d] = gauge[e][d + 1];
          gauge[e][d + 1] = tempval;
        }
      }
    }
  }
  for (int row = 0; row <= 1; row++)
  {
    for (int col = 0; col <=15 ; col++)
    {
      Serial.print(gauge[row][col]);
      Serial.print("\t");
    }
    Serial.println(" ");
  }
}
6

Fantastic :smiley:

7