APIO 11 Guess :D

Author: dolphingarlic

APIO/APIO 11-guess.cpp

@@ -0,0 +1,80 @@
+/*
+APIO 2011 Guess My Word
+- A state in this game consists of the following info:
+    - The set of candidate words (cand)
+    - The set of positions whose letters are already known (mask)
+    - The number of remaining wrong guesses (rem)
+- If |cand| == 0 (i.e. A contradicted themselves), then B wins
+- Otherwise, if rem == 0 (i.e. B made too many wrong guesses),
+  then A wins
+- Otherwise, if |cand| == 1 (i.e. B narrowed the set of words
+  down to a single one), then B wins
+- Otherwise, the following happens:
+    - B must guess a letter present in one of the candidates
+      in a position whose letter is still unknown
+    - A then chooses whether to confirm the letter and in which
+      position, or to tell B that their guess was wrong
+    - If A is able to force a win by using *any* such move
+      *for all* possible letters that B guesses, then A wins;
+      otherwise, B wins
+- No idea what the complexity is, but it's fast enough
+*/
+
+#include <bits/stdc++.h>
+typedef long long ll;
+using namespace std;
+
+string s[1000];
+vector<int> has_len[8];
+
+bool possible(int len, vector<int> cand, int mask, int rem) {
+    if (!cand.size()) return false;
+    if (!rem) return true;
+    if (cand.size() == 1) return false;
+
+    bool good[26];
+    memset(good, 0, sizeof good);
+    for (int i = 0; i < len; i++) if (!(mask & (1 << i))) {
+        for (int j : cand) good[s[j][i] - 'A'] = true;
+    }
+
+    bool all = true;
+    for (char i = 'A'; i <= 'Z'; i++) if (good[i - 'A']) {
+        vector<vector<int>> match(len);
+        vector<int> nomatch;
+        for (int j : cand) {
+            bool found = false;
+            for (int k = 0; k < len && !found; k++) if (s[j][k] == i) {
+                match[k].push_back(j);
+                found = true;
+            }
+            if (!found) nomatch.push_back(j);
+        }
+        bool any = possible(len, nomatch, mask, rem - 1);
+        for (int j = 0; j < len && !any; j++) if (!(mask & (1 << j)))
+             any = possible(len, match[j], mask + (1 << j), rem);
+        all &= any;
+    }
+    return all;
+}
+
+int main() {
+    cin.tie(0)->sync_with_stdio(0);
+    int t;
+    cin >> t;
+    while (t--) {
+        int n;
+        cin >> n;
+        for (int i = 0; i < n; i++) {
+            cin >> s[i];
+            has_len[s[i].size()].push_back(i);
+        }
+        bool any = false;
+        for (int i = 1; i <= 7; i++) {
+            if (!any) any = possible(i, has_len[i], 0, i + 1);
+            has_len[i].clear();
+        }
+        cout << (any ? "Yes" : "No") << '\n';
+    }
+    return 0;
+}