A - XOR Mixup

https://codeforces.com/contest/1698/submission/162060313

Codeforces/1698/A/A.cpp

@@ -0,0 +1,42 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 105;
+
+int t, n, a[N];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> t;
+
+    while (t--) {
+        cin >> n;
+
+        for (int i = 1; i <= n; i++) {
+            cin >> a[i];
+        }
+
+        for (int i = 1; i <= n; i++) {
+            int s = 0;
+
+            for (int j = 1; j <= n; j++) {
+                if (j != i) {
+                    s ^= a[j];
+                }
+            }
+
+            if (s == a[i]) {
+                cout << a[i] << endl;
+
+                break;
+            }
+        }
+    }
+
+    return 0;
+}