div7

contests/silver/2016/january/div7/div7.cpp

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+// #include <bits/stdc++.h> // for some reason the USACO grader doesn't like this for this problem?
+#include <fstream>
+#include <vector>
+using namespace std;
+
+#define MAX_N 50000
+#define ll long long
+
+vector<ll> cows(MAX_N + 1);
+
+int main()
+{
+  ifstream fin("div7.in");
+  ofstream fout("div7.out");
+
+  int N;
+  fin >> N;
+
+  cows[0] = 0;
+
+  for (int i = 1; i <= N; ++i)
+  {
+    fin >> cows[i];
+  }
+
+  for (int i = 1; i <= N; ++i)
+  {
+    cows[i] += cows[i - 1];
+    cows[i] %= 7;
+  }
+
+  vector<int> firstSum(7, -1);
+  int answer = 0;
+  for (int i = 1; i <= N; ++i)
+  {
+    if (firstSum[cows[i]] != -1)
+      answer = max(answer, i - firstSum[cows[i]]);
+    else
+      firstSum[cows[i]] = i;
+  }
+
+  fout << answer << '\n';
+
+  return 0;
+}

contests/silver/2016/january/div7/div7.in

@@ -0,0 +1,8 @@
+7
+3
+5
+1
+6
+2
+14
+10

contests/silver/2016/january/div7/div7.out

@@ -0,0 +1 @@
+5