From 9e6b71af74e41ec8e2da803b98bb9ee15274cd77 Mon Sep 17 00:00:00 2001
From: tiennm99 <tiennm99@outlook.com>
Date: Sat, 29 Nov 2025 02:31:55 +0700
Subject: [PATCH] feat(cpp): add exam (wip)

---
 cpp/exam.cpp | 152 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 152 insertions(+)
 create mode 100644 cpp/exam.cpp

diff --git a/cpp/exam.cpp b/cpp/exam.cpp
new file mode 100644
index 0000000..f647400
--- /dev/null
+++ b/cpp/exam.cpp
@@ -0,0 +1,152 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+using i128 = __int128;
+
+string to_str(i128 x) {
+    if (x == 0) return "0";
+    string s;
+    bool neg = false;
+    if (x < 0) {
+        neg = true;
+        x = -x;
+    }
+    while (x > 0) {
+        s += '0' + (x % 10);
+        x /= 10;
+    }
+    if (neg) s += '-';
+    reverse(s.begin(), s.end());
+    return s;
+}
+
+vector<pair<i128, string> > get_all(int l, int r, const vector<i128> &nums, const vector<string> &num_strs,
+                                    const vector<char> &ops) {
+    if (l == r) {
+        return {{nums[l], num_strs[l]}};
+    }
+    vector<pair<i128, string> > res;
+    for (int m = l; m < r; m++) {
+        auto lefts = get_all(l, m, nums, num_strs, ops);
+        auto rights = get_all(m + 1, r, nums, num_strs, ops);
+        for (auto &le: lefts) {
+            for (auto &ri: rights) {
+                i128 v;
+                char op = ops[m];
+                if (op == '+') v = le.first + ri.first;
+                else if (op == '-') v = le.first - ri.first;
+                else v = le.first * ri.first;
+                string left_str = le.second;
+                if (m > l) left_str = "(" + left_str + ")";
+                string right_str = ri.second;
+                if (r > m + 1) right_str = "(" + right_str + ")";
+                string s = left_str + op + right_str;
+                res.push_back({v, s});
+            }
+        }
+    }
+    return res;
+}
+
+vector<int> matchL, matchR;
+vector<bool> vis;
+
+bool dfs(int u, const vector<vector<int> > &g) {
+    for (int v: g[u]) {
+        if (vis[v]) continue;
+        vis[v] = true;
+        if (matchR[v] == -1 || dfs(matchR[v], g)) {
+            matchL[u] = v;
+            matchR[v] = u;
+            return true;
+        }
+    }
+    return false;
+}
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int n;
+    cin >> n;
+    vector<map<i128, string> > all_poss(n);
+    vector<string> expressions(n);
+    for (int i = 0; i < n; i++) {
+        cin >> expressions[i];
+    }
+
+    for (int i = 0; i < n; i++) {
+        string s = expressions[i];
+        vector<string> num_strs;
+        vector<char> ops;
+        string cur = "";
+        for (char c: s) {
+            if (isdigit(c)) {
+                cur += c;
+            } else {
+                if (!cur.empty()) {
+                    num_strs.push_back(cur);
+                }
+                ops.push_back(c);
+                cur = "";
+            }
+        }
+        if (!cur.empty()) {
+            num_strs.push_back(cur);
+        }
+        int k = num_strs.size();
+        vector<i128> nums(k);
+        for (int j = 0; j < k; j++) {
+            i128 val = 0;
+            for (char d: num_strs[j]) {
+                val = val * 10 + (d - '0');
+            }
+            nums[j] = val;
+        }
+        auto res = get_all(0, k - 1, nums, num_strs, ops);
+        for (auto &p: res) {
+            all_poss[i][p.first] = p.second;
+        }
+    }
+
+    set<i128> all_vals_set;
+    for (auto &mp: all_poss) {
+        for (auto &p: mp) {
+            all_vals_set.insert(p.first);
+        }
+    }
+    vector<i128> id_to_val(all_vals_set.begin(), all_vals_set.end());
+    int m = id_to_val.size();
+    map<i128, int> val_id;
+    for (int j = 0; j < m; j++) {
+        val_id[id_to_val[j]] = j;
+    }
+
+    vector<vector<int> > g(n);
+    for (int i = 0; i < n; i++) {
+        for (auto &p: all_poss[i]) {
+            g[i].push_back(val_id[p.first]);
+        }
+    }
+
+    matchL.assign(n, -1);
+    matchR.assign(m, -1);
+    int cnt = 0;
+    for (int u = 0; u < n; u++) {
+        vis.assign(m, false);
+        if (dfs(u, g)) cnt++;
+    }
+
+    if (cnt == n) {
+        for (int i = 0; i < n; i++) {
+            i128 val = id_to_val[matchL[i]];
+            string s = all_poss[i][val];
+            cout << s << endl;
+        }
+    } else {
+        cout << "NO SOLUTION" << endl;
+    }
+
+    return 0;
+}