Merge branch 'main' of https://github.com/fkdl0048/Algorithm

LeetCode/Combination Sum II.cpp

@@ -0,0 +1,30 @@
+class Solution {
+public:
+    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
+        vector<vector<int>> result;
+        vector<int> currentCombination;
+
+        sort(candidates.begin(), candidates.end());
+        backTrack(candidates, target, 0, currentCombination, result);
+        return result;
+    }
+
+private:
+    void backTrack(vector<int>& candidates, int target, int index, vector<int>& currentCombination, vector<vector<int>>& result) {
+        if (target == 0) {
+            result.push_back(currentCombination);
+            return;
+        }
+
+        if (target < 0) return;
+
+        for (int i = index; i < candidates.size(); i++) {
+
+            if (i > index && candidates[i] == candidates[i - 1]) continue;
+
+            currentCombination.push_back(candidates[i]);
+            backTrack(candidates, target - candidates[i], i + 1, currentCombination, result);
+            currentCombination.pop_back();
+        }
+    }
+};

LeetCode/Combination Sum.cpp

@@ -0,0 +1,27 @@
+class Solution {
+public:
+    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
+        vector<vector<int>> result;
+        vector<int> currentCombiation;
+        backTrack(candidates, 0, target, currentCombiation, result);
+        return result;
+    }
+
+private:
+    void backTrack(vector<int>& candidates, int startIdx, int target, vector<int>& currentCombiation, vector<vector<int>>& result){
+        if (target == 0) {
+            result.push_back(currentCombiation);
+            return;
+        }
+
+        if (target < 0) {
+            return;
+        }
+
+        for (int i = startIdx; i < candidates.size(); i++) {
+            currentCombiation.push_back(candidates[i]);
+            backTrack(candidates, i, target - candidates[i], currentCombiation, result);
+            currentCombiation.pop_back();
+        }
+    }
+};

LeetCode/Count and Say.cpp

@@ -0,0 +1,28 @@
+class Solution {
+public:
+    string countAndSay(int n) {
+        return countAndSayRecursion(n);
+    }
+
+private:
+    string countAndSayRecursion(int n){
+        if (n == 1) return "1";
+
+        string prev = countAndSayRecursion(n - 1);
+        string result = "";
+        int count = 1;
+
+        for (int i = 1; i < prev.size(); i++) {
+            if (prev[i] == prev[i - 1]) {
+                count++;
+            }
+            else {
+                result += to_string(count) + prev[i - 1];
+                count = 1;
+            }
+        }
+        result += to_string(count) + prev.back();
+
+        return result;
+    }
+};

LeetCode/First Missing Positive.cpp

@@ -0,0 +1,23 @@
+class Solution {
+public:
+    int firstMissingPositive(vector<int>& nums) {
+        int n = nums.size();
+
+        // 배열을 정렬하는 대신, 각 숫자를 그 숫자가 있어야 할 위치로 이동
+        for (int i = 0; i < n; ++i) {
+            while (nums[i] > 0 && nums[i] <= n && nums[nums[i] - 1] != nums[i]) {
+                swap(nums[i], nums[nums[i] - 1]);
+            }
+        }
+
+        // 첫 번째로 잘못된 위치의 숫자 찾기
+        for (int i = 0; i < n; ++i) {
+            if (nums[i] != i + 1) {
+                return i + 1;
+            }
+        }
+
+        // 모든 숫자가 제자리에 있을 경우, n + 1이 첫 번째 누락된 양수
+        return n + 1;
+    }
+};

LeetCode/Sudoku Solver.cpp

@@ -0,0 +1,41 @@
+class Solution {
+public:
+    void solveSudoku(vector<vector<char>>& board) {
+        solve(board);
+    }
+private:
+    bool solve(vector<vector<char>>& board) {
+        for (int i = 0; i < 9; i++) {
+            for (int j = 0; j < 9; j++) {
+                if (board[i][j] == '.') {
+                    for (char k = '1'; k <= '9'; k++) {
+                        if (isVaild(board, i, j, k)) {
+                            board[i][j] =  k;
+
+                            if (solve(board)) {
+                                return true;
+                            }
+                            else {
+                                board[i][j] = '.';
+                            }
+                        }
+                    }
+
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    bool isVaild(vector<vector<char>>& board, int i, int j, char k) {
+        for (int idx = 0; idx < 9; idx++){
+            if (board[idx][j] == k) return false;
+            if (board[i][idx] == k) return false;
+            if (board[(i / 3) * 3 + idx / 3][(j / 3) * 3 + idx % 3] == k) return false;
+        }
+
+        return true;
+    }
+};