[ys-han00] WEEK 06 solutions

container-with-most-water/ys-han00.cpp

@@ -0,0 +1,39 @@
+// class Solution {
+// public:
+//     int maxArea(vector<int>& height) {
+//         int n = height.size();
+//         pair<int, int> left_wall = {0, height[0]};
+//         int maxi = -1;
+//         vector<int> dp(n, 0);
+
+//         for(int i = 1; i < n; i++) {
+//             for(int j = 0; j < i; j++) {
+//                 dp[i] = max(dp[i], min(height[i], height[j]) * (i - j));
+//                 if(height[j] > height[i]) 
+//                     break;
+//             }
+//             maxi = max(maxi, dp[i]);
+//         }
+
+//         return maxi;
+//     }
+// };
+
+class Solution {
+public:
+    int maxArea(vector<int>& height) {
+        int left = 0, right = height.size() - 1; 
+        int ans = -1;
+
+        while(left != right) {
+            ans = max(ans, (right - left) * min(height[left], height[right]));
+            if(height[left] < height[right])
+                left++;
+            else
+                right--;
+        }
+
+        return ans;
+    }
+};
+

design-add-and-search-words-data-structure/ys-han00.cpp

@@ -0,0 +1,56 @@
+struct TrieNode {
+    unordered_map<char, TrieNode*> child;
+    bool isEnd;
+    TrieNode() : isEnd(false) {}
+};
+
+class WordDictionary {
+public:
+    TrieNode* root;
+    WordDictionary() {
+        root = new TrieNode();
+    }
+
+    void addWord(string word) {
+        TrieNode* cur = root;
+        for(char c : word) {
+            if(cur->child.find(c) == cur->child.end())
+                cur->child[c] = new TrieNode();
+            cur = cur->child[c];
+        }
+        cur->isEnd = true;
+    }
+
+    bool search(string word) {
+        bool find = false;
+        stack<pair<int, TrieNode*>> sta;
+
+        sta.push({0, root});
+        while(!sta.empty()) {
+            int now = sta.top().first;
+            TrieNode* cur = sta.top().second;
+            sta.pop();
+
+            if(now == word.size() && cur->isEnd)
+                return true;
+
+            if(word[now] == '.') {
+                for(auto mp : cur->child)
+                    sta.push({now + 1, mp.second});
+            } else {
+                if(cur->child.find(word[now]) != cur->child.end())
+                    sta.push({now + 1, cur->child[word[now]]});
+            }
+        }
+
+        return false;
+    }
+};
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * WordDictionary* obj = new WordDictionary();
+ * obj->addWord(word);
+ * bool param_2 = obj->search(word);
+ */
+

longest-increasing-subsequence/ys-han00.cpp

@@ -0,0 +1,38 @@
+// class Solution {
+// public:
+//     int lengthOfLIS(vector<int>& nums) {
+//         int n = nums.size(), maxi, ans = 1;
+//         vector<int> dp(n, 0);
+
+//         dp[0] = 1;
+//         for(int i = 1; i < n; i++) {
+//             maxi = 0;
+//             for(int j = 0; j < i; j++)
+//                 if(nums[j] < nums[i] && maxi < dp[j])
+//                     maxi = dp[j];
+//             dp[i] = maxi + 1;
+//             ans = max(dp[i] , ans);
+//         }
+
+//         return ans;
+//     }
+// };
+
+class Solution {
+public:
+    int lengthOfLIS(vector<int>& nums) {
+        vector<int> sub;
+
+        for(int num : nums) {
+            auto it = lower_bound(sub.begin(), sub.end(), num);
+            int idx = it - sub.begin();
+            if(idx == sub.size())
+                sub.push_back(num);
+            else
+                sub[idx] = num;
+        }
+
+        return sub.size();
+    }
+};
+

spiral-matrix/ys-han00.cpp

@@ -0,0 +1,74 @@
+// class Solution {
+// public:
+//     vector<int> spiralOrder(vector<vector<int>>& matrix) {
+//         int n = matrix.size(), m = matrix[0].size();
+//         vector<int> sorted;
+//         vector<vector<bool>> check(n, vector<bool>(m, false));
+//         queue<pair<int, pair<int, int>>> que;
+
+//         int dx[4] = {-1, 0, 1, 0};
+//         int dy[4] = {0, 1, 0, -1};
+//         // 0: up, 1: right, 2: down, 3: left
+//         que.push({1, {0, 0}});
+//         sorted.push_back(matrix[0][0]);
+//         check[0][0] = true;
+//         while(!que.empty()) {
+//             int d = que.front().first;
+//             int x = que.front().second.first;
+//             int y = que.front().second.second;
+//             que.pop();
+
+//             int new_x = x + dx[d];
+//             int new_y = y + dy[d];
+//             if(new_x >= 0 && new_y >= 0 && new_x < n && new_y < m && check[new_x][new_y] == false) {
+//                 check[new_x][new_y] = true;
+//                 sorted.push_back(matrix[new_x][new_y]);
+//                 que.push({d, {new_x, new_y}});
+//                 continue;
+//             }
+//             d = (d + 1) % 4;
+//             new_x = x + dx[d];
+//             new_y = y + dy[d];
+//             if(new_x >= 0 && new_y >= 0 && new_x < n && new_y < m && check[new_x][new_y] == false) {
+//                 check[new_x][new_y] = true;
+//                 sorted.push_back(matrix[new_x][new_y]);
+//                 que.push({d, {new_x, new_y}});
+//             }
+//         }
+
+//         return sorted;
+//     }
+// };
+
+class Solution {
+public:
+    vector<int> spiralOrder(vector<vector<int>>& matrix) {
+        int n = matrix.size(), m = matrix[0].size();
+        int top = 0, down = n - 1, left = 0, right = m - 1;
+        vector<int> sorted;
+        while(top <= down && left <= right) {
+            for(int i = left; i <= right; i++)
+                sorted.push_back(matrix[top][i]);
+            top++;
+
+            for(int i = top; i <= down; i++)
+                sorted.push_back(matrix[i][right]);
+            right--;
+
+            if(top <= down) {
+                for(int i = right; i >= left; i--)
+                    sorted.push_back(matrix[down][i]);
+                down--;
+            }
+
+            if(left <= right) {
+                for(int i = down; i >= top; i--)
+                    sorted.push_back(matrix[i][left]);
+                left++;
+            }
+        }
+
+        return sorted;
+    }
+};
+

valid-parentheses/ys-han00.cpp

@@ -0,0 +1,27 @@
+class Solution {
+public:
+    bool isValid(string s) {
+        stack<char> sta;
+
+        for(char c : s) {
+            if(c == '(' || c == '[' || c == '{') {
+                sta.push(c);
+                continue;
+            }
+
+            if(sta.empty())
+                sta.push(c);
+            else if(c == ')' && sta.top() == '(')
+                sta.pop();
+            else if(c == ']' && sta.top() == '[')
+                sta.pop();
+            else if(c == '}' && sta.top() == '{')
+                sta.pop();
+            else
+                sta.push(c);
+        }
+
+        return (sta.empty() ? true : false);
+    }
+};
+