舞蹈链模板 Dancing Links

来源:互联网 发布:手抄报健康知识知多少 编辑:程序博客网 时间:2024/03/29 02:57

矩阵从1开始,判断是否可以完全覆盖:g.Dance(0)

const int maxnode = 100010;const int MaxM = 1010;const int MaxN = 1010;struct DLX { //四向链表int n, m, size; //n行,m列;元素上下左右对应指针int U[maxnode], D[maxnode], L[maxnode], R[maxnode], Row[maxnode], Col[maxnode];int H[MaxN], S[MaxM]; //S为每列元素个数, H指向每行末尾元素int ansd, ans[MaxN]; //ansd为解的行数void init(int _n, int _m) { //初始化n = _n;m = _m;for (int i = 0; i <= m; i++) {S[i] = 0;U[i] = D[i] = i;L[i] = i - 1;R[i] = i + 1;}R[m] = 0; L[0] = m;size = m;for (int i = 1; i <= n; i++)H[i] = -1;}void Link(int r, int c) { //添加++S[Col[++size] = c];Row[size] = r;D[size] = D[c];U[D[c]] = size;U[size] = c;D[c] = size;if (H[r] < 0)H[r] = L[size] = R[size] = size;else {R[size] = R[H[r]];L[R[H[r]]] = size;L[size] = H[r];R[H[r]] = size;}}void remove(int c) { //删除一列L[R[c]] = L[c]; R[L[c]] = R[c];for (int i = D[c]; i != c; i = D[i])for (int j = R[i]; j != i; j = R[j]) {U[D[j]] = U[j];D[U[j]] = D[j];--S[Col[j]];}}void resume(int c) { //恢复一列for (int i = U[c]; i != c; i = U[i])for (int j = L[i]; j != i; j = L[j])++S[Col[U[D[j]] = D[U[j]] = j]];L[R[c]] = R[L[c]] = c;}bool Dance(int d) { //d为递归深度if (R[0] == 0) {ansd = d;return true;}int c = R[0];for (int i = R[0]; i != 0; i = R[i])if (S[i] < S[c])c = i;remove(c);for (int i = D[c]; i != c; i = D[i]) {ans[d] = Row[i];for (int j = R[i]; j != i; j = R[j]) remove(Col[j]);if (Dance(d + 1))return true;for (int j = L[i]; j != i; j = L[j]) resume(Col[j]);}resume(c);return false;}}g;