Aug25: DP and state problem [H]

... ... >_

daily/Aug25.cc

@@ -0,0 +1,53 @@
+#include <functional>
+#include <vector>
+using namespace std;
+
+class Solution {
+ public:
+  /**
+   * @brief LC698: partition to K equal sum subsets
+   * Time: O(N * 2^N), Space: O(2^N), DP
+   *
+   * @param nums
+   * @param k
+   * @return true
+   * @return false
+   */
+  bool canPartitionKSubsets(vector<int>& nums, int k) {
+    int sum = 0;
+    for (int num : nums) {
+      sum += num;
+    }
+    if (sum % k != 0) {
+      return false;
+    }
+    int per = sum / k;
+    sort(nums.begin(), nums.end());
+    if (nums.back() > per) {
+      return false;
+    }
+    int len = nums.size();
+    vector<bool> dp(1 << len, true);
+    // function<bool(int, int)> dfs = [&](int s, int p) -> bool {
+    function<bool(int, int)> dfs = [&](int s, int p) -> bool {
+      if (s == 0) return true;
+
+      if (!dp[s]) return dp[s];
+
+      dp[s] = false;
+      for (int i = 0; i < len; i++) {
+        if (nums[i] + p > per) {
+          break;
+        }
+        if ((s >> i) & 1) {
+          if (dfs(s ^ (1 << i), (p + nums[i]) % per)) {
+            return true;
+          }
+        }
+      }
+      return false;
+    };
+
+    return dfs((1 << len) - 1, 0);
+  }
+};