1#include <iostream>2#include <string>3using namespace std;4 5char base[64];6char table[256];7 8void init()9{10    for (int i = 0; i < 26; i++) base[i] = 'A' + i;11    for (int i = 0; i < 26; i++) base[26 + i] = 'a' + i;12    for (int i = 0; i < 10; i++) base[52 + i] = '0' + i;13    base[62] = '+', base[63] = '/';14 15    for (int i = 0; i < 256; i++) table[i] = 0xff;16    for (int i = 0; i < 64; i++) table[base[i]] = i;17    table['='] = 0;18}19 20string decode(string str)21{22    string ret;23    int i;24    for (i = 0; i < str.size(); i += 4) {25        ret += table[str[i]] << 2 | table[str[i + 1]] >> 4;26        if (str[i + 2] != '=')27            ret += (table[str[i + 1]] & 0x0f) << 4 | table[str[i + 2]] >> 2;28        if (str[i + 3] != '=')29            ret += table[str[i + 2]] << 6 | table[str[i + 3]];30    }31    return ret;32}33 34int main()35{36    init();37    cout << int(table[0]) << endl;38 39    string str;40    cin >> str;41    cout << decode(str) << endl;42    return 0;43}