leetcode第361场周赛补题

7020. 统计对称整数的数目 - 力扣（LeetCode）

思路：转化为字符串后枚举

class Solution {
public:
    int countSymmetricIntegers(int low, int high) {
        int res = 0;
        for(int i = low; i <= high; i ++ )
        {
            string s = to_string(i);
            if(s.size() % 2) continue;
            int pre = 0, suf = 0;
            for(int i = 0; i < s.size() / 2; i ++ ) pre += s[i] - 'a';
            for(int i = s.size() / 2; i < s.size(); i ++ ) suf += s[i] - 'a';
            res += (pre == suf);
        }
        return res;
    }
};

8040. 生成特殊数字的最少操作 - 力扣（LeetCode）

思路：枚举，rfind()

class Solution {
public:
    int minimumOperations(string num) {
        int n = num.size();
        auto f = [&](string tail) {
            int i = num.rfind(tail[1]);
            if(i == string::npos || i == 0) return n;
            i = num.rfind(tail[0], i - 1);
            if(i == string::npos) return n;
            return n - i - 2;
        };
        return min({n - (num.find('0') != string::npos), f("00"), f("25"), f("50"), f("75")});
    }
};