题解 | #进制转换2#

#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <vector>

using namespace std;

/**
 * char转int
 * @param target
 * @return
 */
int char2Int(char target);

/**
 * int转char
 * @param target
 * @return
 */
char int2Char(int target);

/**
 * 将m进制的num转化为十进制
 * @param num
 * @param m
 */
long long convertM2Ten(string num, int m);

/**
 * 将十进制的num转化为n进制
 * @param num
 * @param n
 */
void convertTen2N(long long num, int n);

/**
 * 进制转换2--清华大学
 * @return
 */
int main() {
    int m, n;
    while (cin >> m >> n) {
        string num;
        cin >> num;
        long long number = convertM2Ten(num, m);
        convertTen2N(number, n);
    }

    return 0;
}

long long convertM2Ten(string num, int m) {
    long long number = 0;
    for (int i = 0; i < num.size(); ++i) {
        number *= m;
        number += char2Int(num[i]);
    }
    return number;
}

void convertTen2N(long long num, int n) {
    vector<char> ans;
    if (num == 0) {
        //特殊情况
        ans.push_back('0');
    } else {
        while (num != 0) {
            ans.push_back(int2Char(num % n));
            num /= n;
        }
    }

    for (int i = ans.size() - 1; i >= 0; --i) {
        cout << ans[i];
    }
    cout << endl;
}

char int2Char(int target) {
    if (target < 10) {
        return target + '0';
    } else {
        //题目备注已经说明，输出为小写字母
        return target - 10 + 'a';
    }
}

int char2Int(char target) {
    if ('0' <= target && target <= '9') {
        //0~9直接减去字符0即可
        return target - '0';
    } else {
        //大于等于10，则先减去字符A（注意题目是大写还是小写），再加上10
        return target - 'A' + 10;
    }
}