USACO2.1.5 Hamming Codes (hamming)

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数据范围很小所以dfs。
每次从当前的最大数+1向上枚举，与之前的所有数字比较，如果可以则记录。

/*ID:shijiey1PROG:hammingLANG:C++*/#include <cstdio>#include <cstring>#include <algorithm>#include <vector>using namespace std;int n, b, d;vector<int> ans;bool cmp(int a, int b) {int cnt = 0;while (a || b) {cnt += ((a & 1) ^ (b & 1));a >>= 1;b >>= 1;}return cnt >= d;}void dfs(int i, int step) {ans.push_back(i);if (step == n) {for (int j = 0; j < ans.size(); j++) {if (!((j + 1) % 10 - 1) && j) printf("\n");else if (j) printf(" ");printf("%d", ans[j]);}printf("\n");exit(0);}for (int j = i + 1; j < 1 << b; j++) {bool flag = true;for (int k = 0; k < ans.size(); k++) {flag = cmp(ans[k], j);if (!flag) break;}if (flag) {dfs(j, step + 1);break;}}}int main() {freopen("hamming.in", "r", stdin);freopen("hamming.out", "w", stdout);scanf("%d %d %d", &n, &b, &d);dfs(0, 1);return 0;}

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