1189. Maximum Number of Balloons*

​​https://leetcode.com/problems/maximum-number-of-balloons/​​

题目描述

Given a string ​​text​​​, you want to use the characters of ​​text​​ to form as many instances of the word “balloon” as possible.

You can use each character in ​​text​​ at most once. Return the maximum number of instances that can be formed.

Example 1:

Input: text = "nlaebolko"
Output: 1

Example 2:

Input: text = "loonbalxballpoon"
Output: 2

Example 3:

Input: text = "leetcode"
Output: 0

Constraints:

  • ​​1 <= text.length <= 10^4​​
  • ​​text​​ consists of lower case English letters only.

C++ 实现 1

统计 ​​text​​ 里的每个字符的个数, 看它们能组成多少个 “balloon”.

我还在 LeetCode 的讨论区写了个回答: ​​[C++] Easy To Understand Solution​​

class Solution {
public:
    int maxNumberOfBalloons(string text) {
        unordered_map<char, int> record;
        for (auto &c : text) record[c] ++;
        int count = 0, i = 0;
        string target = "balloon";
        while (true) {
            int idx = i % target.size();
            if (record[target[idx]] == 0) break;
            if (idx == target.size() - 1) count ++;
            record[target[idx]] --;
            ++ i;
        }
        return count;
    }
};

C++ 实现 2

看讨论区中很多答案是检查组成 “balloon” 的字符个数够不够, 取其中字符个数最小值.

class Solution {
public:
    int maxNumberOfBalloons(string text) {
        unordered_map<char, int> mm;
        for (auto &i : text) mm[i] += 1;
        return min(mm['b'], min(mm['a'], min(mm['l']/2, min(mm['o']/2, mm['n']))));
    }
};