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+// 1146. Snapshot Array
+#include "leetcode.h"
+
+/*
+ * implement a 'SnapshotArray' class that supports the following interface
+ * - 'SnapshotArray(int length)' initialises an array-like data structure with
+ * the given length. initially, each element equals zero.
+ * - 'void set(index, val)' sets the element at the given 'index' to be equal to
+ * 'val'
+ * - 'int snap()' takes a snapshot of the array and retusn the 'snap_id': the
+ * total number of times we called 'snap()' minus 1
+ * - 'int get(index, snap_id)' returns the value at the given 'index', at the
+ * time we took the snapshot with the given 'snap_id'
+ */
+
+class SnapshotArray {
+ int curr_snap = 0;
+ vector<vector<pair<int, int>>> vvp;
+
+public:
+ SnapshotArray(int length) { vvp = vector<vector<pair<int, int>>>(length); }
+ void set(int index, int val) {
+ if (vvp[index].empty() || vvp[index].back().first != curr_snap)
+ vvp[index].push_back({curr_snap, val});
+ else
+ vvp[index].back().second = val;
+ }
+ int snap() { return curr_snap++; }
+ int get(int index, int snap_id) {
+ auto i = upper_bound(begin(vvp[index]), end(vvp[index]),
+ pair<int, int>(snap_id, INT_MAX));
+ return i == begin(vvp[index]) ? 0 : prev(i)->second;
+ }
+};
+
+int main() {
+ SnapshotArray *obj = new SnapshotArray(3);
+ obj->set(0, 5);
+ printf("%d\n", obj->snap()); // expect: 0
+ obj->set(0, 6);
+ printf("%d\n", obj->get(0, 0)); // expect: 5
+}