You can start by creating an empty dictionary to store each athlete's score as the key and their rank as the value. Then, sort the given array in descending order and iterate through it. For the first 3 athletes, assign their respective medals as their rank. For the rest of the athletes, use their placement number as their rank. Finally, populate the answer array with each athlete's rank using the dictionary. Here's the code:

```
def findRanks(score):
    rank_dict = {}
    for i in range(len(score)):
        rank_dict[score[i]] = 0
        
    sorted_scores = sorted(score, reverse=True)
    
    for i in range(len(sorted_scores)):
        if i == 0:
            rank_dict[sorted_scores[i]] = "Gold Medal"
        elif i == 1:
            rank_dict[sorted_scores[i]] = "Silver Medal"
        elif i == 2:
            rank_dict[sorted_scores[i]] = "Bronze Medal"
        else:
            rank_dict[sorted_scores[i]] = str(i+1)
            
    answer = []
    for i in range(len(score)):
        answer.append(rank_dict[score[i]])
        
    return answer
```

You can then call `findRanks` with an array of scores, like this:

```
scores = [10, 5, 15, 20, 25]
ranks = findRanks(scores)
print(ranks) # outputs ["Silver Medal", "5", "Bronze Medal", "Gold Medal", "1"]
```
You are given an integer array score of size n, where score[i] is the score of the ith athlete in a competition. All the scores are guaranteed to be unique.

The athletes are placed based on their scores, where the 1st place athlete has the highest score, the 2nd place athlete has the 2nd highest score, and so on. The placement of each athlete determines their rank:

- The 1st place athlete's rank is "Gold Medal".
- The 2nd place athlete's rank is "Silver Medal".
- The 3rd place athlete's rank is "Bronze Medal".
- For the 4th place to the nth place athlete, their rank is their placement number (i.e., the xth place athlete's rank is "x").

Return an array answer of size n where answer[i] is the rank of the ith athlete.