[Leetcode] 506. Relative Ranks 解题报告

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本文介绍了一种算法，用于根据运动员的成绩确定其相对排名，并为前三名颁发金牌、银牌和铜牌。该算法首先将所有成绩进行排序，然后根据排序结果返回相应的奖牌名称或排名。

题目：

Given scores of N athletes, find their relative ranks and the people with the top three highest scores, who will be awarded medals: "Gold Medal", "Silver Medal" and "Bronze Medal".

Example 1:

Input: [5, 4, 3, 2, 1]
Output: ["Gold Medal", "Silver Medal", "Bronze Medal", "4", "5"]
Explanation: The first three athletes got the top three highest scores, so they got "Gold Medal", "Silver Medal" and "Bronze Medal". 
For the left two athletes, you just need to output their relative ranks according to their scores.

Note:

N is a positive integer and won't exceed 10,000.
All the scores of athletes are guaranteed to be unique.

思路：

既可以直接做全排序，也可以用大顶堆或者优先级队列。不过时间复杂度都是O(nlogn)。我这里用了全排序，代码看起来更清爽一些。

代码：

class Solution {
public:
    vector<string> findRelativeRanks(vector<int>& nums) {
        vector<pair<int, int>> ranks;
        vector<string> ret(nums.size(), "");
        for (int i = 0; i < nums.size(); ++i) {
            ranks.push_back(make_pair(nums[i], i));
        }
        sort(ranks.begin(), ranks.end());
        reverse(ranks.begin(), ranks.end());
        for (int i = 0; i < ranks.size(); ++i) {
            if (i == 0) {
                ret[ranks[i].second] = "Gold Medal";
            }
            else if (i == 1) {
                ret[ranks[i].second] = "Silver Medal";
            }
            else if (i == 2) {
                ret[ranks[i].second] = "Bronze Medal";
            }
            else {
                ret[ranks[i].second] = to_string(i + 1);
            }
        }
        return ret;
    }
};