【USACO】2017 December Contest, Platinum题解

【比赛经历】

【T1】Standing Out from the Herd

【题目链接】

【题解链接】

【思路要点】

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN    200005
#define MAXC    26
template <typename T> void read(T &x) {x = 0; int f = 1;char c = getchar();for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';x *= f;
}
template <typename T> void write(T x) {if (x < 0) x = -x, putchar('-');if (x > 9) write(x / 10);putchar(x % 10 + '0');
}
template <typename T> void writeln(T x) {write(x);puts("");
}
struct Suffix_Automaton {int child[MAXN][MAXC];int father[MAXN], depth[MAXN];int root, size, last, n;vector <int> a[MAXN];int colour[MAXN];bool unq[MAXN];long long ans[MAXN];int new_node(int dep) {depth[size] = dep;unq[size] = true;return size++;}void init() {size = 0;root = last = new_node(0);}void addcol(int pos, int col) {if (!unq[pos]) return;if (colour[pos] == 0) colour[pos] = col;else if (col != colour[pos]) unq[pos] = false;}void Extend(int ch, int col) {int np = child[last][ch];if (np) {if (depth[np] == depth[last] + 1)  {addcol(np, col);last = np;} else {int nq = new_node(depth[last] + 1);father[nq] = father[np];father[np] = nq;memcpy(child[nq], child[np], sizeof(child[np]));for (int p = last; child[p][ch] == np; p = father[p])child[p][ch] = nq;addcol(nq, col);last = nq;}} else {int np = new_node(depth[last] + 1);int p = last;for (; child[p][ch] == 0; p = father[p])child[p][ch] = np;if (child[p][ch] == np) {addcol(np, col);last = np;return;}int q = child[p][ch];if (depth[q] == depth[p] + 1) {father[np] = q;addcol(np, col);last = np;return;} else {int nq = new_node(depth[p] + 1);father[nq] = father[q];father[np] = father[q] = nq;memcpy(child[nq], child[q], sizeof(child[q]));for (; child[p][ch] == q; p = father[p])child[p][ch] = nq;addcol(np, col);last = np;}}}void insert(char *s, int col) {int len = strlen(s + 1);last = root; ans[col] = 0;for (int i = 1; i <= len; i++)Extend(s[i] - 'a', col);n = col;}void work(int pos) {for (unsigned i = 0; i < a[pos].size(); i++) {work(a[pos][i]);if (unq[a[pos][i]]) addcol(pos, colour[a[pos][i]]);else unq[pos] = false;}if (pos != 0 && unq[pos]) ans[colour[pos]] += depth[pos] - depth[father[pos]];}void solve() {for (int i = 1; i < size; i++)a[father[i]].push_back(i);work(0);for (int i = 1; i <= n; i++)printf("%lld\n", ans[i]);}
} SAM;
char s[MAXN];
int main() {freopen("standingout.in", "r", stdin);freopen("standingout.out", "w", stdout);SAM.init();int n; read(n);for (int i = 1; i <= n; i++) {scanf("%s", s + 1);SAM.insert(s, i);}SAM.solve();return 0;
}

【T2】Push a Box

【题目链接】

【题解链接】

【思路要点】

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN    1505
template <typename T> void read(T &x) {x = 0; int f = 1;char c = getchar();for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';x *= f;
}
template <typename T> void write(T x) {if (x < 0) x = -x, putchar('-');if (x > 9) write(x / 10);putchar(x % 10 + '0');
}
template <typename T> void writeln(T x) {write(x);puts("");
}
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};
int pr[4] = {1, 0, 3, 2};
//0: Right, 1: Left, 2: Down, 3: Up.
char mp[MAXN][MAXN];
int n, m, q, sx, sy, tx, ty, sd;
int num[MAXN][MAXN], col[MAXN][MAXN][4];
int timer, dfn[MAXN][MAXN], low[MAXN][MAXN];
bool tv[MAXN][MAXN], visited[MAXN][MAXN][4];
bool valid(char x) {return x == '.' || x == 'A' || x == 'B';
}
void work(int px, int py, int fx, int fy, int fd) {dfn[px][py] = low[px][py] = ++timer;int tmp = 0;if (fd != -1) {col[px][py][fd] = ++tmp;for (int j = 0; j <= 3; j++) {int tx = px + dx[j];int ty = py + dy[j];if (!valid(mp[tx][ty])) continue;if (dfn[tx][ty] && col[px][py][j] == 0)col[px][py][j] = tmp;}}for (int i = 0; i <= 3; i++) {int tx = px + dx[i];int ty = py + dy[i];if (tx == fx && ty == fy) continue;if (!valid(mp[tx][ty])) continue;if (dfn[tx][ty]) {low[px][py] = min(low[px][py], dfn[tx][ty]);continue;}work(tx, ty, px, py, pr[i]);low[px][py] = min(low[px][py], low[tx][ty]);if (low[tx][ty] >= dfn[px][py]) {col[px][py][i] = ++tmp;for (int j = i + 1; j <= 3; j++) {int tx = px + dx[j];int ty = py + dy[j];if (!valid(mp[tx][ty])) continue;if (dfn[tx][ty] && col[px][py][j] == 0)col[px][py][j] = tmp;}} else {col[px][py][i] = 1;for (int j = i + 1; j <= 3; j++) {int tx = px + dx[j];int ty = py + dy[j];if (!valid(mp[tx][ty])) continue;if (dfn[tx][ty] && col[px][py][j] == 0)col[px][py][j] = 1;}}}
}
void printcol() {for (int i = 1; i <= n; i++) {for (int j = 1; j <= m; j++) {for (int k = 0; k <= 3; k++)printf("%d", col[i][j][k]);printf(" ");}printf("\n");}
}
void getsd(int px, int py, int ld) {tv[px][py] = true;if (px == tx && py == ty) sd = ld;for (int i = 0; i <= 3; i++) {int tx = px + dx[i];int ty = py + dy[i];if (!valid(mp[tx][ty]) || tv[tx][ty]) continue;getsd(tx, ty, pr[i]);}
}
void dfs(int px, int py, int ld) {visited[px][py][ld] = true;int td = pr[ld];if (valid(mp[px + dx[td]][py + dy[td]]) && !visited[px + dx[td]][py + dy[td]][ld]) {dfs(px + dx[td], py + dy[td], ld);}for (int i = 0; i <= 3; i++)if (!visited[px][py][i] && col[px][py][i] == col[px][py][ld]) {dfs(px, py, i);}
}
void printvis() {for (int i = 1; i <= n; i++) {for (int j = 1; j <= m; j++) {for (int k = 0; k <= 3; k++)printf("%d", visited[i][j][k]);printf(" ");}printf("\n");}
}
int main() {freopen("pushabox.in", "r", stdin);freopen("pushabox.out", "w", stdout);read(n), read(m), read(q);for (int i = 1; i <= n; i++)scanf("%s", mp[i] + 1);for (int i = 1; i <= n; i++)for (int j = 1; j <= m; j++)if (dfn[i][j] == 0 && mp[i][j] != '#') {work(i, j, 0, 0, -1);}for (int i = 1; i <= n; i++)for (int j = 1; j <= n; j++) {if (mp[i][j] == 'A') sx = i, sy = j;if (mp[i][j] == 'B') tx = i, ty = j;}sd = -1;getsd(sx, sy, -1);if (sd == -1) visited[tx][ty][0] = true;else dfs(tx, ty, sd);for (int i = 1; i <= q; i++) {int x, y;read(x), read(y);bool flg = false;for (int j = 0; j <= 3; j++)flg |= visited[x][y][j];if (flg) printf("YES\n");else printf("NO\n");}return 0;
}

【T3】Greedy Gift Takers

【题目链接】

【题解链接】

【思路要点】

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN    200005
template <typename T> void read(T &x) {x = 0; int f = 1;char c = getchar();for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';x *= f;
}
template <typename T> void write(T x) {if (x < 0) x = -x, putchar('-');if (x > 9) write(x / 10);putchar(x % 10 + '0');
}
template <typename T> void writeln(T x) {write(x);puts("");
}
struct SegmentTree {struct Node {int lc, rc;int Min, tag;} a[MAXN];int n, root, size;void pushdown(int root) {if (a[root].tag) {int tmp = a[root].tag, pos;pos = a[root].lc;a[pos].Min -= tmp;a[pos].tag += tmp;pos = a[root].rc;a[pos].Min -= tmp;a[pos].tag += tmp;a[root].tag = 0;}}void update(int root) {a[root].Min = min(a[a[root].lc].Min, a[a[root].rc].Min);}void build(int &root, int l, int r) {root = ++size;if (l == r) {a[root].Min = n - l;return;}int mid = (l + r) / 2;build(a[root].lc, l, mid);build(a[root].rc, mid + 1, r); update(root);}void init(int x) {n = x; size = root = 0;build(root, 0, n - 1);}void modify(int root, int l, int r, int ql, int qr, int d) {if (l == ql && r == qr) {a[root].tag += d;a[root].Min -= d;return;}pushdown(root);int mid = (l + r) / 2;if (mid >= ql) modify(a[root].lc, l, mid, ql, min(mid, qr), d);if (mid + 1 <= qr) modify(a[root].rc, mid + 1, r, max(mid + 1, ql), qr, d);update(root);}void solve(int x) {modify(root, 0, n - 1, 0, x, 1);}int query() {return a[root].Min;}
} SMT;
int main() {freopen("greedy.in", "r", stdin);freopen("greedy.out", "w", stdout);int n; read(n);SMT.init(n);for (int i = 1; i <= n; i++) {int x; read(x);SMT.solve(x);if (SMT.query() == 0) {printf("%d\n", n - i);return 0;}}return 0;
}

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