HDU 3715 Go Deeper (2-sat)

HDU 3715 Go Deeper

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Test instructions: Constructs an X array according to the test instructions function. Q Maximum Recursive layer number

Idea: Convert to 2-sat problem, because X can only be 0. 1,c can only be 0, 1. 2 So the problem is good to do, for 0, 1, 2 corresponding to 3 kinds of expression, and then the depth of two, engage 2-sat can

Code:

#include <cstdio> #include <cstring> #include <cstdlib> #include <vector> #include < algorithm>using namespace Std;const int maxnode = 205;struct twoset {int n;vector<int> g[maxnode * 2];bool Mark[M Axnode * 2];int S[maxnode * 2], sn;void init (int tot) {n = tot * 2;for (int i = 0; i < n; i + = 2) {g[i].clear (); g[i^1]. Clear ();} Memset (Mark, False, sizeof);} void Add_edge (int u, int uval, int v, int vval) {u = u * 2 + uval;v = v * 2 + vval;g[u^1].push_back (v); G[v^1].push_back (U) ;} void Delete_edge (int u, int uval, int v, int vval) {u = u * 2 + uval;v = v * 2 + vval;g[u^1].pop_back (); G[v^1].pop_back (); }bool dfs (int u) {if (mark[u^1]) return false;if (Mark[u]) return true;mark[u] = true; s[sn++] = u;for (int i = 0; i < g[u].size (); i++) {int v = g[u][i];if (!dfs (v)) return false;} return true;} BOOL Solve () {for (int i = 0; i < n, i + = 2) {if (!mark[i] &&!mark[i + 1]) {sn = 0;if (!dfs (i)) {for (int j = 0) ; J < SN; J + +) Mark[s[j]] = FALSE;SN =0;if (!dfs (i + 1)) return false;}}} return true;}}  gao;const int N = 10005;int T, N, M;int A[n], B[n], c[n];bool judge (int dep) {gao.init (n); for (int i = 0; i < dep; i++) {if (c[i] = = 0) Gao.add_edge (a[i], 1, b[i], 1); else if (c[i] = = 1) {Gao.add_edge (A[i], 0, A[i], 1); Gao.add_edge (A[i], 0, b [i], 1); Gao.add_edge (B[i], 0, A[i], 1); Gao.add_edge (B[i], 0, B[i], 1);} Elsegao.add_edge (A[i], 0, B[i], 0);} return Gao.solve ();} int main () {scanf ("%d", &t), while (t--) {scanf ("%d%d", &n, &m), for (int i = 0; i < m; i++) scanf ("%d%d%d", & Amp;a[i], &b[i], &c[i]); int l = 0, r = m + 1;while (L < r) {int mid = (L + R)/2;if (judge (mid)) L = mid + 1;e LSE r = Mid;} printf ("%d\n", L-1);} return 0;}

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HDU 3715 Go Deeper (2-sat)