add code2interview 剑指offer

Author: bbruceyuan

code4interview/c++/面试题03. 数组中重复的数字.cpp

@@ -0,0 +1,51 @@
+#include <iostream>
+#include <utility>
+#include <vector>
+#include <unordered_map>
+using namespace std;
+
+// 每次都可以先自己定义一个 MyException
+class MyException: public exception {
+public:
+    std::string s;
+    explicit MyException(std::string str): s(std::move(str)) {};
+    const char* what() const noexcept override {return s.c_str();};
+};
+
+
+
+class Solution {
+public:
+    int findRepeatNumber(vector<int>& nums) {
+        for (std::size_t i = 0; i < nums.size(); i++) {
+            while (nums[i] != i) {
+                if (nums[nums[i]] != nums[i])
+                    std::swap(nums[i], nums[nums[i]]);
+                else
+                    return nums[i];
+            }
+        }
+        // 如果满足题目要求，这里不会到达
+        // throw MyException("不能运行到这里");
+        return -1;
+    }
+
+    int findRepeatNumber2(vector<int>& nums) {
+        // 可以直接使用 hash map
+        unordered_map<int, bool> m;
+        for (auto i: nums) {
+            if (m.find(i) == m.end()) {
+                m[i] = true;
+            } else
+                return i;
+        }
+        throw MyException("不可能到达这里");
+    }
+};
+
+int main() {
+    vector<int> nums {0, 2, 2};
+    cout << Solution::findRepeatNumber(nums) << endl;
+    cout << Solution::findRepeatNumber2(nums) << endl;
+    return 0;
+}

code4interview/c++/面试题04. 二维数组中的查找.cpp

@@ -0,0 +1,83 @@
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+class Solution {
+public:
+    bool findNumberIn2DArray(vector<vector<int>>& matrix, int target) {
+        // 直接暴力遍历每一个数字
+        bool flag = false;
+        for (const auto& v: matrix) {
+            // v 是一个 arr
+            for (const auto& i: v) {
+                if (i == target) {
+                    flag = true;
+                }
+            }
+        }
+        return flag;
+
+    }
+    bool findNumberIn2DArray2(vector<vector<int>> &matrix, int target) {
+        // 这这个使用 数组规律做题
+        if (matrix.empty()) return false;
+        int colIdx = 0, rowIdx = int(matrix.size()) - 1;
+        while (colIdx < matrix[0].size() && rowIdx >= 0) {
+            if (matrix[rowIdx][colIdx] == target) {
+                return true;
+            } else if (matrix[rowIdx][colIdx] > target) {
+                rowIdx--;
+            } else {
+                colIdx++;
+            }
+        }
+        return false;
+    }
+
+    int findNumberIn2DArray3(vector<vector<int>> &matrix, int target) {
+        // 还可以使用二分法做题
+        // 这种方法其实并不建议
+        // TODO: 需要 Debug
+
+        if (matrix.empty() or matrix[0].empty())
+            return false;
+
+        int low = 0, high = int(matrix.size()) -1;
+        int mid;
+        while (low < high) {
+            mid = low + (high - low + 1) / 2;
+            if (matrix[mid][0] > target)
+                high = mid -1;
+            else
+                low = mid;
+        }
+        int rowIdx = low;
+        int left = 0, right = (int)matrix[0].size() -1;
+        while (left < right) {
+            mid = left + (right - left + 1) / 2;
+            if (matrix[rowIdx][mid] > target) {
+                right = mid -1;
+            } else
+                left = mid;
+        }
+        // 这个时候 left 一定等于 right
+        return matrix[rowIdx][left] == target;
+    }
+};
+
+int main() {
+    Solution solution;
+    vector<vector<int>> nums {
+            {1,   4,  7, 11, 15},
+            {2,   5,  8, 12, 19},
+            {3,   6,  9, 16, 22},
+            {10, 13, 14, 17, 24},
+            {18, 21, 23, 26, 30}};
+
+//    vector<vector<int>> nums;
+//    cout << solution.findNumberIn2DArray(nums, 9) << endl;
+//    cout << solution.findNumberIn2DArray2(nums, 3) << endl;
+    cout << solution.findNumberIn2DArray3(nums, 5) << endl;
+    return 0;
+}

code4interview/c++/面试题05. 替换空格.cpp

@@ -0,0 +1,50 @@
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+class Solution {
+public:
+    string replaceSpace(string s) {
+        string::size_type pos(0);
+        while (true) {
+            if((pos=s.find(' ', pos))!=string::npos) {
+                s.replace(pos,1,"%20");//替换
+                pos += 3;
+            }
+            else break;
+        }
+        return s;
+    }
+
+    string replaceSpace2(string s) {
+        if (s.empty()) return s;
+        int spaceCount = 0;
+        for (const auto & i: s) {
+            if (i == ' ')spaceCount++;
+        }
+        std::size_t oldLen = s.size();
+
+        std::size_t newLen = s.size() + spaceCount * 2;
+        s.resize(newLen);
+        while (oldLen != newLen) {
+            --oldLen;
+            if (s[oldLen] == ' ') {
+                s[--newLen] = '0';
+                s[--newLen] = '2';
+                s[--newLen] = '%';
+            } else
+                s[--newLen] = s[oldLen];
+        }
+        return s;
+    }
+};
+
+int main() {
+    Solution solution;
+    string s = "hello  world";
+
+    cout << solution.replaceSpace2(
+            "We are happy.") << endl;
+    return 0;
+}

code4interview/c++/面试题06. 从尾到头打印链表.cpp

@@ -0,0 +1,77 @@
+#include <string>
+#include <vector>
+#include <algorithm>
+#include <stack>
+#include <iostream>
+using namespace std;
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+
+
+struct ListNode {
+    int val;
+    ListNode *next;
+    explicit ListNode(int x) : val(x), next(nullptr) {}
+};
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> reversePrint(ListNode* head) {
+        vector<int> res;
+        stack<int> s;
+        while(head) {
+            s.push(head->val);
+            head = head->next;
+        }
+        while (!s.empty()) {
+            res.push_back(s.top());
+            s.pop();
+        }
+        
+        return res;
+    }
+
+    vector<int> reversePrint2(ListNode *head) {
+        vector<int> res;
+        reversePrintRecursive(head, res);
+        return res;
+    }
+
+    void reversePrintRecursive(ListNode *head, vector<int> &res) {
+        // 这是一个辅助函数
+        if (head == nullptr) return;
+        reversePrintRecursive(head->next, res);
+        res.push_back(head->val);
+    }
+};
+
+int main() {
+    Solution solution;
+    auto *head = new ListNode(0);
+    auto cur = head;
+    for (int i = 0; i < 5; i++) {
+        cur->next = new ListNode(i);
+        cur = cur->next;
+    }
+    cur->next = nullptr;
+    vector<int> res = solution.reversePrint2(head->next);
+    for (auto i: res) {
+        cout << i << endl;
+    }
+    return 0;
+}

code4interview/c++/面试题07. 重建二叉树.cpp

@@ -0,0 +1,88 @@
+#include <string>
+#include <vector>
+#include <algorithm>
+#include <stack>
+#include <iostream>
+using namespace std;
+
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+
+struct TreeNode {
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    explicit TreeNode(int x): val(x), left(nullptr), right(nullptr) {}
+};
+
+
+class Solution {
+public:
+    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
+        // 找到中止条件
+        if (preorder.empty()) return nullptr;
+
+        // 首先简历树的根节点
+        auto root = new TreeNode(preorder[0]);
+        // 下一步是获取 左子树的 preorder 和 inorder
+        auto it = std::find(inorder.begin(), inorder.end(), preorder[0]);
+
+        vector<int> leftInOrder(inorder.begin(), it);
+        // 不能包括第一个数字
+        vector<int> rightInOrder(it + 1, inorder.end());
+
+        vector<int> leftPreOrder(preorder.begin() + 1, preorder.begin() + 1 + leftInOrder.size());
+        vector<int> rightPreOrder(preorder.begin() + 1 + leftInOrder.size(), preorder.end());
+
+        root->left = buildTree(leftPreOrder, leftInOrder);
+        root->right = buildTree(rightPreOrder, rightInOrder);
+        return root;
+    }
+
+    TreeNode* buildTreeNoRecursive(vector<int>& preorder, vector<int>& inorder) {
+        if (preorder.empty()) return nullptr;
+        stack<TreeNode*> roots;
+        std::size_t pre = 0, in = 0;
+
+        auto root = new TreeNode(preorder[pre]);
+        auto returnRoot = root;
+        roots.push(root);
+        pre++;
+
+        while (pre < preorder.size()) {
+            if (root->val == inorder[in]) {
+                while (!roots.empty() && roots.top()->val == inorder[in]) {
+                    root = roots.top();
+                    roots.pop();
+                    in++;
+                }
+                root->right = new TreeNode(preorder[pre]);
+                root = root->right;
+                roots.push(root);
+                pre++;
+            } else {
+                root->left = new TreeNode(preorder[pre]);
+                root = root->left;
+                roots.push(root);
+                pre++;
+            }
+        }
+        return returnRoot;
+    }
+
+};
+
+int main() {
+    Solution solution;
+    vector<int> preorder{3,5, 9,10, 20,15,7}, inorder{9,5, 10, 3,15,20,7};
+    solution.buildTreeNoRecursive(preorder, inorder);
+    return 0;
+}