s0491

src/s0491_non_decreasing_subsequences.cpp

@@ -0,0 +1,31 @@
+#include "s0491_non_decreasing_subsequences.hpp"
+
+void findSubsequencesDFS(vector<int> &subsequences, vector<vector<int>> &result,
+                         vector<int> &nums, int startIndex) {
+  int size = nums.size();
+  // 结束条件
+  if (startIndex == size) return;
+
+  // 初始化一个哈希表用来存储元素是否在数层中使用过
+  unordered_map<int, bool> used;
+
+  for (int i = startIndex; i < size; ++i) {
+    // 剪枝，如果元素在数层中使用过则跳过
+    if (used.count(nums[i]) == 1) continue;
+    // 当当前元素大于等于起始元素之前的元素时，将它添加进去
+    if (startIndex == 0 || nums[i] >= nums[startIndex - 1]) {
+      subsequences.push_back(nums[i]);
+      if (subsequences.size() > 1) result.push_back(subsequences);
+      used[nums[i]] = true;
+      findSubsequencesDFS(subsequences, result, nums, i + 1);
+      subsequences.pop_back();
+    }
+  }
+}
+
+vector<vector<int>> S0491::findSubsequences(vector<int> &nums) {
+  vector<int> subsequences{};
+  vector<vector<int>> result{};
+  findSubsequencesDFS(subsequences, result, nums, 0);
+  return result;
+}