• • • • • 傳送門
        • 思路
        • 參考代碼

傳送門

思路

按位貪心。但是我太弱了，明明可以 O(n) O ( n ) 預處理，我卻只會 O(32n) O ( 32 n ) ，唉，我太弱啦！

參考代碼

懶得改了。還是留意一下能夠預處理的內容吧。

#include <cstdio> #include <cstdlib> #include <cmath> #include <cstring> #include <cassert> #include <cctype> #include <climits> #include <ctime> #include <iostream> #include <algorithm> #include <vector> #include <string> #include <stack> #include <queue> #include <deque> #include <map> #include <set> #include <bitset> #include <list> #include <functional> typedef long long LL; typedef unsigned long long ULL; using std::cin; using std::cout; using std::endl; typedef int INT_PUT; INT_PUT readIn() {INT_PUT a = 0; bool positive = true;char ch = getchar();while (!(ch == '-' || std::isdigit(ch))) ch = getchar();if (ch == '-') { positive = false; ch = getchar(); }while (std::isdigit(ch)) { a = a * 10 - (ch - '0'); ch = getchar(); }return positive ? -a : a; } void printOut(INT_PUT x) {char buffer[20]; int length = 0;if (x < 0) putchar('-'); else x = -x;do buffer[length++] = -(x % 10) + '0'; while (x /= 10);do putchar(buffer[--length]); while (length); }const int maxn = int(1e5) + 5; int n, m; int ans; struct Instruction {enum{AND, OR, XOR};int type;int val;void read(){char str[10];scanf("%s", str);if (str[0] == 'A')type = AND;else if (str[0] == 'O')type = OR;else if (str[0] == 'X')type = XOR;val = readIn();}int calc(int input){if (type == AND)return input & val;else if (type == OR)return input | val;elsereturn input ^ val;} } ins[maxn];int calc(int input) {for (int i = 1; i <= n; i++)input = ins[i].calc(input);return input; }void run() {n = readIn();m = readIn();for (int i = 1; i <= n; i++)ins[i].read();int through = calc(0);for (int i = 30; ~i; i--){if ((ans | (1 << i)) > m)continue;int v = calc(1 << i);if ((v & (1 << i)) > (through & (1 << i)))ans |= 1 << i;}printOut(calc(ans)); }int main() {run();return 0; }

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