Leetcode--regular Expression Matching

Implement regular expression matching with support for ‘.‘ and ‘*‘ .

entire input string (not partial). The function prototype should be:bool IsMatch (const char *s, const char *p) Some examples:ismatch ("AA", "a") →falseismatch ( "AA", "AA") →trueismatch ("AAA", "AA") →falseismatch ("AA", "A *") →trueismatch ("AA", ". *") →trueismatch ("AB", ". *") →true IsMatch ("AaB", "C*a*b") →true

This paper uses the method of regular expression matching, simulates the string p with the non-deterministic state automata, and then matches the string, and the time complexity of the algorithm is O (N);

Problem Solving Code:

Class Graph{private:struct Node{int wei;node* next;}; node* g;int v;bool* marked;void dfs (const int s) {Marked[s] = true;vector<int> temp = adj (s); for (int i=0; I&LT;TEMP.S Ize (); i++) {if (!marked[temp[i])) DFS (Temp[i]);} return;} Public:graph (const int v) {this->v = v;marked = new Bool[v];g = new node[v];for (int i=0; i<v; i++) {Marked[i] = false; G[i].wei = 0;g[i].next = nullptr;}} ~graph () {delete[] marked;for (int i=0; i<v; i++) {node* Temp1 = G[i].next;while (temp1!=nullptr) {node* temp2 = Temp1; Temp1 = Temp1->next;delete Temp2;}} Delete[] g;} BOOL is_marked (const int v) {return marked[v];} void restore_marked () {for (int i=0; i<v; i++) marked[i] = false;} void Add_edge (const int V, const int W) {node* temp = new Node;temp->wei = W;temp->next = G[v].next;g[v].next = temp; }void Dfs (vector<int>& start) {int n = start.size (); for (int i=0; i<n; i++) if (!marked[start[i]]) DFS (start[i ]);} vector<int>& adj (const int v) {vector<int>* res = new Vector<int>;node* temp = g[v].next;while (temp!=nullptr) {res->push_back (temp->wei); temp = Temp->next;} return *res;}; Class Solution {Public:bool isMatch (const char *s, const char *p) {if (Has_star (p)) return match (s,p); int I=0;while (s[i]!= ' \ && P[i]! = ' + ') {if (s[i]== '. ' | | p[i]== '. ') {i++;continue;} if (s[i]! = P[i]) return false;i++;} if (s[i]!= ' | | | p[i]!= ') return False;return true;} BOOL Match (const char* s, const char* p) {String temp_s = char_to_string (s); string temp_p = Char_to_string (p); int n = temp_ P.length (); graph G (n+1); for (int i=0; i<n; i++) {if (p[i] = = ' * ') {G.add_edge (i,i-1); G.add_edge (i-1,i); G.add_edge (i,i +1);}} vector<int> pc;vector<int> marked;marked.push_back (0); G.dfs (marked); for (int i=0; i<n+1; i++) {if (g.is _marked (i)) pc.push_back (i); for (int i=0; I<temp_s.length (), i++) {marked.clear (); for (int v=0; v<pc.size (); v++) {if (pc[v]<n) {if (P[pc[v]] = = S[i] | | P[PC[V]] = = '. ') Marked.push_back (pc[v]+1);}} Pc.clear (); g.restore_marked (); G.dfs (marked); for (int i=0; i<n+1; i++) {if (g.is_marked (i)) pc.push_back (i);}} for (int i=0; i<pc.size (); i++) {if (pc[i] = = N) return true; return false;} BOOL Has_star (const char* s) {int i=0;while (s[i]! = ' + ') {if (s[i] = = ' * ') return true;i++;} return false;} String char_to_string (const char* s) {String temp = ""; int i=0;while (s[i]! = ' + ') {temp = temp + s[i];i++;} return temp;};

Leetcode--regular Expression Matching