(贪心, 字符串, 位运算)Codeforces Round #402 E. Bitwise Formula

题目网址: Codeforces Round #402 E. Bitwise Formula

题意分析:

• 题意:

  • 给n个长度为m的二进制变量赋值, 其中有计算位运算后赋值, 且有未知’?’变量, 求’?’为 何值时, 使得所有变量和最大, 何值时, 使得所有变量和最小.

• 思路:

  • 模拟题, 且从最高位开始判断 加 ‘0’ 还是 加 ‘1’

代码:(just_sortb博主写的)

#include <bits/stdc++.h>using namespace std;const int maxn = 5005;map <string, int> mp;struct Q {    string s;    int num, a, b, op;} q[maxn];int n, m;int cal(int x, int p) {    q[0].num = p;    int ans = 0;    for (int i = 1; i <= n; i++)     {        if (q[i].op == 0) q[i].num = q[i].s[x] - '0';        else         {            int a = q[q[i].a].num, b = q[q[i].b].num;            if (q[i].op == 1) q[i].num = a & b;            if (q[i].op == 2) q[i].num = a | b;            if (q[i].op == 3) q[i].num = a ^ b;        }        ans += q[i].num;    }    return ans;}int main(){    cin >> n >> m;    string s;    mp["?"] = 0;    for (int i = 1; i <= n; i++)     {        cin >> s;        mp[s] = i;        cin >> s;        cin >> s;        if (isdigit(s[0]))         {            q[i].op = 0;            q[i].s = s;        }        else {            q[i].a = mp[s];            cin >> s;            if (s[0] == 'A') q[i].op = 1;            if (s[0] == 'O') q[i].op = 2;            if (s[0] == 'X') q[i].op = 3;            cin >> s;            q[i].b = mp[s];        }    }    string ans1 = "", ans2 = "";    for (int i = 0; i < m; i++)     {        int cnt1 = cal(i, 0);        int cnt2 = cal(i, 1);        if (cnt1 <= cnt2) ans1 += '0'; else ans1 += '1';        if (cnt1 >= cnt2) ans2 += '0'; else ans2 += '1';    }    cout << ans1 << endl;    cout << ans2 << endl;    return 0;}