feat(src): add 90-subsetsWithDup, 91-numDecodings

Author: kwu130

src/90-subsetsWithDup.cpp

@@ -0,0 +1,56 @@
+//
+// Created by 1412 on 2025/11/21.
+//
+
+#include <bits/stdc++.h>
+#include "../include/common.h"
+
+using namespace std;
+
+class Solution {
+public:
+    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
+        vector<vector<int>> res;
+        ranges::sort(nums);
+        dfs(nums, 0, {}, res);
+        return res;
+    }
+
+private:
+    void dfs(vector<int>& nums, int index, vector<int>&& path, vector<vector<int>>& res) {
+        res.emplace_back(path);
+        for (int i = index; i < nums.size(); ++i) {
+            if (i > index && nums[i] == nums[i - 1]) {
+                continue;
+            }
+            path.emplace_back(nums[i]);
+            dfs(nums, i + 1, std::move(path), res);
+            path.pop_back();
+        }
+    }
+};
+
+void test() {
+    Solution s;
+    vector<int> nums = {1, 2, 2};
+    vector<vector<int>> expected = {
+        {},
+        {1},
+        {1, 2},
+        {1, 2, 2},
+        {2},
+        {2, 2}
+    };
+    vector<vector<int>> res = s.subsetsWithDup(nums);
+    assert(compareHelper::equalIgnoreOrder(res, expected));
+
+    nums = {0};
+    expected = {{}, {0}};
+    res = s.subsetsWithDup(nums);
+    assert(compareHelper::equalIgnoreOrder(res, expected));
+}
+
+int main() {
+    test();
+    return 0;
+}

src/91-numDecodings.cpp

@@ -0,0 +1,41 @@
+//
+// Created by 1412 on 2025/11/21.
+//
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class Solution {
+public:
+    int numDecodings(string s) {
+        vector<int> dp(s.size() + 1, 0);
+        dp[0] = 1;  // ""
+        if (s[0] == '0') {
+            dp[1] = 0;
+        } else {
+            dp[1] = 1;
+        }
+        for (int i = 2; i <= s.size(); i++) {
+            if (s[i - 1] != '0') {
+                dp[i] += dp[i - 1];
+            }
+            if (s[i - 2] == '1' || (s[i - 2] == '2' && s[i - 1] <= '6')) {
+                dp[i] += dp[i - 2];
+            }
+        }
+        return dp[s.size()];
+    }
+};
+
+void test() {
+    Solution s;
+    assert(s.numDecodings("12") == 2);
+    assert(s.numDecodings("226") == 3);
+    assert(s.numDecodings("06") == 0);
+}
+
+int main() {
+    test();
+    return 0;
+}