Merge pull request kothariji#601 from Kowsihan-sk/master

added leetcode longest duplicate substring problem

Author: kothariji

Graph/(LEETCODE) Shortest_path_in_binary_matrix.cpp

@@ -0,0 +1,38 @@
+class Solution {
+public:
+    
+    int shortestPathBinaryMatrix(vector<vector<int>>& grid) {
+        int n = grid.size(), len = 1;
+        if(grid[0][0] == 1 || grid[n-1][n-1] == 1) return -1;
+        if(n==1) return 1;
+        
+        vector<vector<int>> off = {{0,1},{0,-1},{1,0},{-1,0},{1,1},{-1,-1},{1,-1},{-1,1}};
+        queue<pair<int,int>> q;
+        q.push({0,0});
+        grid[0][0] = 1;
+        
+        int sz, row, col, i, j;
+        
+        while(!q.empty()){
+            sz = q.size();
+            for(i = 0; i < sz; i++){
+                row = q.front().first, col = q.front().second;
+                q.pop();
+                
+                if(row == n-1 && col == n-1) return len;
+                
+                for(j = 0; j < 8; j++){
+                    int x = row + off[j][0], y = col + off[j][1];
+                    if(x >= 0 && y >= 0 && x < n && y < n && grid[x][y] == 0){
+                        grid[x][y] = 1;
+                        q.push({x,y});
+                    }
+                }
+                
+            }
+            len++;
+        }
+        
+        return -1;
+    }
+};

Leetcode - Top Interview Questions/1044_Longest_duplicate_substring.cpp

@@ -0,0 +1,57 @@
+vector<unsigned long long> roll;
+
+class Solution {
+public:
+    bool match(string s, int n, int sz, string &ans){
+        unordered_map<unsigned long long, vector<int>> mp;
+        unsigned long long hash = 0;
+        for(int i = 0; i < sz; i++)
+            hash = (hash*31 + (s[i] - 'a'));
+        
+        mp[hash].push_back(0);
+        
+        for(int i = sz; i < n; i++){
+            hash = (hash - roll[sz - 1]*(s[i - sz] - 'a'));
+            hash = (hash*31 + (s[i] - 'a'));
+            
+            if(mp.count(hash)){
+                for(int v : mp[hash]){
+                    string t = s.substr(v, sz), c = s.substr(i - sz + 1, sz);
+                    if(t.compare(c) == 0){
+                        ans = t;
+                        return true;
+                    }
+                }
+            }
+            mp[hash].push_back(i - sz + 1);
+        }
+        
+        return false;
+    }
+    string longestDupSubstring(string s) {
+        int n = s.length();
+        if(n == 0) return "";
+        
+        roll.resize(n);
+        roll[0] = 1;
+        for(int i = 1; i < n; i++)
+            roll[i] = (31*roll[i-1]);
+        
+        string ans = "", temp;
+        int l = 1, h = n, mid;
+        bool flag = false;
+        
+        while(l <= h){
+            temp = "";
+            mid = l + (h-l)/2;
+            flag = match(s, n, mid, temp);
+            if(flag){
+                if(ans.size() < temp.size())
+                    ans = temp;
+                l = mid+1;
+            }else h = mid - 1;
+        }
+        
+        return ans;
+    }
+};