c - How to find the 2nd largest number in the array, but return the last index that the value appears in? -

my actual problem find number in data set 2nd highest frequency. i'm initializing array size of largest number in data set , incrementing corresponding indexes in array each time number appears in data set. if more 2 indexes shares 2nd highest frequency need return larger index. code returns correct answer in cases, not , having trouble finding error in logic.

int secondfreq(int data[], int maxnum){     int highest = 0;     int secondhighest = 0;     int x;      for(x = 0; x < maxnum; x++){         if(data[x] > data[highest]){             secondhighest = highest;             highest = x;         }         else if (data[x] > data[secondhighest]){             secondhighest = x;         }         else if (data[x] == data[secondhighest]){             secondhighest = x;         }     }      return secondhighest + 1; } 

here example of array yields wrong answer. left number index , right number value stored @ index. function returns 12 (11th index+1), should returning 5 (4th index + 1).

    0 - 2     1 - 2     2 - 5     3 - 2     4 - 5     5 - 4     6 - 2     7 - 2     8 - 6     9 - 4     10 - 3     11 - 6     12 - 2     13 - 2     14 - 3 

your code has 2 problems:

1. you need set highest = x; in case of data[x] == data[highest].
2. secondhighest should pending.

the following example modification:

int secondfreq(int data[], int maxnum){     int highest = 0;     int secondhighest, secondflag = 0;//secondflag : whether secondhighest has been determined, 0 : undetermined, 1(not 0) : determined     int x;      for(x = 1; x < maxnum; x++){         if(data[x] > data[highest]){             secondhighest = highest;             highest = x;             secondflag = 1;         }         else if (data[x] == data[highest]){             highest = x;         }         else if (secondflag == 0 || data[x] >= data[secondhighest]){             secondhighest = x;             secondflag = 1;         }     }      if(secondflag)         return secondhighest + 1;     else         return 0;//all elements same }