P1143 进制转换

https://www.luogu.com.cn/training/117#problems

尝试去复健。今天意外收获ac。

大致思路：将进制转为10进制数后再尝试转成其他进制的数即可。

/*

*/
#include <bits/stdc++.h>
#define debug(x) cout << #x << "=" << x << endl
#define endl '\n'
#define rep(i, a, b) for(int i = a; i <= b; i ++)
using namespace std;
typedef pair<int, int> pii;
using ll = long long;
const int N = 2e5 + 5, INF = 0x3f3f3f3f;

map<int, char> num2char;
map<char, int> char2num;

void init(){
	
	for(int i = 0; i <= 9; i ++){
		num2char[i] = (char)(i + '0');
		char2num[(char)(i + '0')] = i;
	}
	
	for(int i = 10; i <= 15; i ++){
		num2char[i] = (char)(i - 10 + 'A');
		char2num[(char)(i - 10 + 'A')] = i;
	}
}

void solve(){
	init();
	int a;
	cin >> a;
	
	string s;
	cin >> s;
	
	int b;
	cin >> b;
	
	string ans;
	
	int n10 = 0;
	int t = 0;
	for(int i = s.size() - 1; i >= 0; i --) {
		int now = char2num[s[i]];
		n10 += now * pow(a, t ++);
	}
	
	while(n10 > 0) {
		ans.push_back(num2char[n10 % b]);
		n10 /= b;
	}
	
	for(int i = ans.size() - 1; i >= 0; i --) cout << ans[i] ;
	
}

int main(){
	cin.tie(0);cout.tie(0);ios::sync_with_stdio(0);
	#ifdef LOCAL
	FILE *pPp = fopen("1input.txt", "a+");fclose(pPp);
	freopen("1input.txt", "r", stdin);
	//freopen("1output.txt", "w", stdout);
	#endif
	solve();
	
	
	return 0;
}