洛谷P2447 [SDOI2010]外星千足虫(异或方程组)
作者:互联网
题意
Sol
异或高斯消元的板子题。
bitset优化一下,复杂度\(O(\frac{nm}{32})\)
找最优解可以考虑高斯消元的过程,因为异或的特殊性质,每次向下找的时候找到第一个1然后交换就行,这样显然是最优的
#include<bits/stdc++.h>
using namespace std;
const int MAXN = 2001;
inline int read() {
char c = getchar(); int x = 0, f = 1;
while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
return x * f;
}
int N, M;
bitset<MAXN> b[MAXN];
void Gauss() {
int ans = 0;
for(int i = 1; i <= N; i++) {
int j = i;
while(!b[j][i] && j < M + 1)
j++;
if(j == M + 1) {puts("Cannot Determine"); return ;}
ans = max(ans, j);
swap(b[i], b[j]);
for(int j = 1; j <= M; j++) {
if(i == j || !b[j][i]) continue;
b[j] ^= b[i];
}
}
printf("%d\n", ans);
for(int i = 1; i <= N; i++)
puts(!b[i][N + 1] ? "Earth" : "?y7M#");
}
int main() {
N = read(); M = read();
for(int i = 1; i <= M; i++) {
string s; cin >> s;
b[i][N + 1] = read();
for(int j = 1; j <= N; j++) b[i][j] = (s[j - 1] == '0' ? 0 : 1);
}
Gauss();
return 0;
}
标签:洛谷,千足虫,int,while,SDOI2010,read,异或,高斯消,getchar 来源: https://www.cnblogs.com/zwfymqz/p/10357719.html