ABC 252, in process of making c, got idea but got sidetracked

atcoder/beginner_contests/252/c.cpp

@@ -0,0 +1,51 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+
+int main(){
+    ios::sync_with_stdio(0);
+    cin.tie(0);
+
+    int n;
+    cin >> n;
+
+    vector<map<int, int>> reels(n);
+
+    for(int i = 0; i < n; ++i){
+        long long reel_in;
+        cin >> reel_in;
+
+        for(int j = 9; j >= 0; --j){
+            int l = reel_in % 10;
+            reel_in /= 10;
+
+            reels[i][l] = j;
+        }
+    }
+
+    set<int> button_presses;
+    int min_time = 100000;
+
+    for(int i = 0; i < 10; ++i){
+        button_presses.clear();
+
+        for(int j = 0; j < n; ++j){
+            int time = reels[i][j];
+            while(button_presses.count(time)){
+                time += 10;
+            }
+            button_presses.insert(time);
+
+            if(time < min_time){
+                min_time = time;
+            }
+        }
+    }
+
+    cout << min_time << endl;
+
+    cout << flush;
+
+    return 0;
+}