21/03/03 Codeforces Educational Round 105

- a: stack, brute force
- b: math

Author: seunghyukcho

codeforces/edu/105/a.cpp

@@ -0,0 +1,43 @@
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+int main() {
+    int t;
+    for(cin >> t; t > 0; t--) {
+        string s;
+        cin >> s;
+
+        int cnt[3] = {0, 0, 0};
+        for(char ch: s) cnt[ch - 'A']++;
+
+        char bracket[3] = {')', ')', ')'};
+        bracket[s[0] - 'A'] = '(';
+
+        bool ans = false;
+        for(int i = 0; i < 3 && !ans; i++) {
+            if(cnt[i] == cnt[(i + 1) % 3] + cnt[(i + 2) % 3]) {
+                ans = true;
+                if(bracket[i] == '(') bracket[(i + 1) % 3] = bracket[(i + 2) % 3] = ')';
+                else {
+                    bracket[i] = ')';
+                    bracket[(i + 1) % 3] = bracket[(i + 2) % 3] = '(';
+                }
+            }
+        }
+
+        int st = 0;
+        for(int i = 0; i < s.size() && ans; i++) {
+            char ch = bracket[s[i] - 'A'];
+            if(ch == '(') st++;
+            else if(st == 0) ans = false;
+            else st--;
+        }
+
+        if(ans && st == 0) cout << "YES\n";
+        else cout << "NO\n";
+    }
+
+    return 0;
+}

codeforces/edu/105/b.cpp

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+#include <iostream>
+#include <algorithm>
+
+using namespace std;
+
+int main() {
+    int t;
+    for(cin >> t; t > 0; t--) {
+        int n, colored[4];
+        cin >> n;
+        for(int i = 0; i < 4; i++) cin >> colored[i];
+
+        bool ans = true;
+        for(int i = 0; i < 4 && ans; i++) {
+            int prev = i, here = (i + 1) % 4, next = (i + 2) % 4, opposite = (i + 3) % 4;
+            if(colored[here] <= n - 2) continue;
+            else {
+                ans = max(colored[here] - n + 2, 0) + max(colored[opposite] - n + 2, 0) <= min(colored[prev], 2) + min(colored[next], 2);
+                if(colored[here] == n) ans = ans && colored[prev] > 0 && colored[next] > 0;
+            } 
+        }
+
+        cout << (ans ? "YES" : "NO") << '\n';
+    }
+}

codeforces/edu/105/c.cpp

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+#include <iostream>
+#include <vector>
+#include <algorithm>
+#include <queue>
+
+using namespace std;
+
+int solve(vector<int> &a, vector<int> &b) {
+    int ans = 0, nbox = 1, pivot = 0, match = 0;
+    vector<int> consecutive(b.size());
+    vector<bool> matched(a.size(), false);
+
+    consecutive[b.size() - 1] = 1;
+    for(int i = b.size() - 2; i >= 0; i--) {
+        if(b[i] + 1 == b[i + 1])
+            consecutive[i] = consecutive[i + 1] + 1;
+        else
+            consecutive[i] = 1;
+    }
+
+    for(int i = 0; i < a.size(); i++) {
+        if(binary_search(b.begin(), b.end(), a[i])) {
+            matched[i] = true;
+            match++;
+        }
+    }
+
+    ans = match;
+    queue<int> q;
+    while(pivot < b.size()) {
+
+    }
+
+    return ans;
+}
+
+int main() {
+    int t;
+    for(cin >> t; t > 0; t--) {
+        int n, m;
+        cin >> n >> m;
+
+        vector<int> ap, an, bp, bn;
+        for(int i = 0; i < n; i++) {
+            int num;
+            cin >> num;
+
+            if(num > 0) ap.push_back(num);
+            else an.push_back(num);
+        }
+
+        for(int i = 0; i < m; i++) {
+            int num;
+            cin >> num;
+
+            if(num > 0) bp.push_back(num);
+            else bn.push_back(num);
+        }
+    }
+}