add KMP cpp and build BST

KMP/KMP.cpp

@@ -0,0 +1,47 @@
+#include<iostream>
+#include<vector>
+using namespace std;
+void kmp(string T, string P);
+vector<int> preprocess(string P);
+int main()
+{
+    string T = "sagertehg";
+    string P = "ge";
+    kmp(T, P);
+    return 0;
+}
+
+void kmp(string T, string P){
+    T = " " + T;
+    P = " " + P;
+    vector<int> prefix = preprocess(P);
+    int k = 0;
+    for(int i = 1; i < T.length(); ++i){
+        while(k > 0 && P[k + 1] != T[i]){
+            k = prefix[k];
+        }
+        if(P[k + 1] == T[i]){
+            k += 1;
+        }
+        if(k == P.length() - 1){
+            cout << "find match at "<<i <<endl;
+            k = prefix[k];
+        }
+    }
+}
+
+vector<int> preprocess(string P){
+    int k = 0;
+    vector<int> res(P.length());
+    res[1] = 0;
+    for(int i = 2; i < P.length();++i){
+        while(k >0 && P[k + 1] != P[i]){
+            k = res[k];
+        }
+
+        if(P[k + 1] == P[i])
+            k += 1;
+        res[i] = k;
+    }
+    return res;
+}

RebuildBST.cpp

@@ -0,0 +1,98 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+class Node{
+public:
+    int val;
+    Node *left;
+    Node *right;
+    Node(int v): val(v){
+        left = NULL;
+        right = NULL;
+    }
+};
+
+Node* convert(vector<int> &vec, int start, int end);
+void preOrderTraverse(Node* root);
+void inOrderTraverse(Node* root);
+Node* convert2(vector<int>&vec, int parentVal);
+Node* newConvert(vector<int>&vec);
+
+int main(){
+    int arr[] ={10, 7, 5, 9, 8, 15, 12};
+    int len = sizeof(arr) / sizeof(int);
+    vector<int> vec1(&arr[0], &arr[len]);
+    Node* res1 = convert(vec1, 0, len - 1);  // O(N^2)
+    vector<int> vec2(&arr[0], &arr[len]);    // O(N)
+    Node* res2 = newConvert(vec2);
+    cout << "Preorder traverse of BST generated by two methods: " << endl;
+    preOrderTraverse(res1);
+    cout << endl;
+    preOrderTraverse(res2);
+    cout << endl << endl;
+    cout << "Inorder traverse of BST generated by two methods:" << endl;
+    inOrderTraverse(res1);
+    cout << endl;
+    inOrderTraverse(res2);
+    cout << endl << endl;
+    return 0;
+}
+
+Node* convert(vector<int> &vec, int start, int end){ // O(N^2)
+    if(start > end) return NULL;
+    int rootVal = vec[start];
+    Node* root = new Node(rootVal);
+    int index = end + 1;
+    for(int i = start + 1; i <= end; ++i){
+        if(vec[i] > rootVal){
+            index = i;
+            break;
+        }
+    }
+    root->left = convert(vec, start + 1, index - 1);
+    root->right = convert(vec, index, end);
+    return root;
+}
+
+Node* newConvert(vector<int>& vec){
+    int rootVal = vec[0];
+    Node* root = new Node(rootVal);
+    vec.erase(vec.begin());
+    if(rootVal > vec[0]){
+        root -> left = convert2(vec, rootVal);   // call convert2 method
+    }
+    if(rootVal < vec[0]){
+        root -> right = convert2(vec, rootVal);  // call convert2 method
+    }
+    return root;
+}
+
+Node* convert2(vector<int> &vec, int parentVal){  // O(N)
+    if(vec.size() == 0) return NULL;
+    int rootVal = vec[0];
+    Node* root = new Node(rootVal);
+    vec.erase(vec.begin());                       // erase the first element
+    if(rootVal > vec[0]){
+        root -> left = convert2(vec, rootVal);
+    }
+    if(vec[0] < parentVal && rootVal < vec[0]){   // compare with parent value
+        root -> right = convert2(vec, rootVal);
+    }
+    return root;
+}
+
+void preOrderTraverse(Node* root){
+    if(root == NULL) return;
+    cout << root->val << ", ";
+    preOrderTraverse(root->left);
+    preOrderTraverse(root->right);
+}
+
+void inOrderTraverse(Node* root){
+    if(root == NULL) return;
+    inOrderTraverse(root->left);
+    cout << root->val << ", ";
+    inOrderTraverse(root->right);
+}