I'm fairly new to java and have been stuck on this assignment in which I had to create three functions (mean, median and mode) and return and print the mean, median and mode. I completed the mean and median but am stuck on the mode. My code runs correctly if there is one mode but it doesn't print out multiple modes and I would also like it to output a blank space if there are no modes.

private static int mode(int [] arr){ // Function calculates mode  
  int mf = -1, maxcount = 0, i, j; // Declaring Variables
    
    for (i = 0; i < arr.length; i  ){
      int count = 0; // Current count
        
        for (j = i   1; j < arr.length; j  ){
          if(arr[i] == arr[j]){ // Compares indexes
            count  ; // Increments count by 1
          }
        }
        if(count > maxcount){
          maxcount = count;
          mf = arr[i];
        }
    }
    if(mf == -1){
      return 0;
    } else {
      return mf;
    }

}

CodePudding user response：

Here as you're using two for loops the complexity becomes O(n^2). You can do it in just O(n) as an improvement as you need.

private int[] mode(int[] arr) {
    if(arr.length==0) return new int[]{};
    Map<Integer, Integer> map=new HashMap<>();
    int maxCount=0;
    int maxVal=0;
    for(int i: arr) {
        int curr=map.getOrDefault(i, 0);
        if(curr 1==maxVal) {
            maxCount  ;
        } else if(curr 1>maxVal) {
            maxCount=1;
            maxVal=curr 1;
        }
        map.put(i, curr 1);
    }
    int[] resu=new int[maxCount];
    int j=0;        
    Iterator<Integer> it=map.keySet().iterator();
    while(it.hasNext()) {
        int v=it.next();
        if(map.get(v)==maxVal) {
            resu[j]=v;
            j  ;
        }
    }
    return resu;
}

Here, if the input array is empty, we are returning empty array. Furthermore if you have any idea on the input array range, instead of using a map, we can use an array as well (if the range is less).

private int[] mode(int[] arr) {
    if(arr.length==0) return new int[]{};
    int[] track=new int[100]; // range, here considering 0-99
    int maxCount=0;
    int maxVal=0;
    for(int i: arr) {
          track[i];
        if(track[i]>maxVal) {
            maxVal=track[i];
            maxCount=1;
        } else if(track[i]==maxVal) {
            maxCount  ;
        }
    }
    int[] resu=new int[maxCount];
    int j=0;
    for(int i=0; i<track.length; i  ) {
        if(track[i]==maxVal) {
            resu[j]=i;
            j  ;
        }
    }
    return resu;
}

CodePudding user response：

Your mode() method is right. Just you have to put condition in main method. If array return 0 then print No Mode Found otherwise get mode.

Here down is condition:

public static void main(String[] args) {
     int arr[] = {0, 6, 7, 2, 8};
     String foundOrNot = (mode(arr) == 0) ? "No Mode Found" : String.valueOf(mode(arr));
     System.out.println(foundOrNot);
}