Merge pull request #110 from AkashSingh19/master

Added Solution of N queen in cpp

Author: PawanJaiswal08

51.N Queen.cpp

@@ -0,0 +1,59 @@
+class Solution {
+  public:
+    bool isSafe1(int row, int col, vector < string > board, int n) {
+      // check upper element
+      int duprow = row;
+      int dupcol = col;
+      
+      //check upper left diagonal
+      while (row >= 0 && col >= 0) {
+        if (board[row][col] == 'Q')
+          return false;
+        row--;
+        col--;
+      }
+
+      col = dupcol;
+      row = duprow;
+      //check left col on the same row
+      while (col >= 0) {
+        if (board[row][col] == 'Q')
+          return false;
+        col--;
+      }
+
+      row = duprow;
+      col = dupcol;
+      //check lower left diagonal
+      while (row < n && col >= 0) {
+        if (board[row][col] == 'Q')
+          return false;
+        row++;
+        col--;
+      }
+      return true;
+    }
+
+  public:
+    void solve(int col, vector < string > & board, vector < vector < string >> & ans, int n)     {
+      if (col == n) {
+        ans.push_back(board);
+        return;
+      }
+      for (int row = 0; row < n; row++) {
+        if (isSafe1(row, col, board, n)) {
+          board[row][col] = 'Q';
+          solve(col + 1, board, ans, n);
+          board[row][col] = '.';
+        }
+      }
+    }
+
+  public:
+    vector < vector < string >> solveNQueens(int n) {
+      vector < vector < string >> ans;
+      vector < string > board(n, string(n,'.'));
+      solve(0, board, ans, n);
+      return ans;
+    }
+};

71.Simplify Path.cpp

@@ -0,0 +1,15 @@
+class Solution {
+public:
+   string simplifyPath(string path) {
+    string res, tmp;
+    vector<string> stk;
+    stringstream ss(path);
+    while(getline(ss,tmp,'/')) {
+        if (tmp == "" or tmp == ".") continue;
+        if (tmp == ".." and !stk.empty()) stk.pop_back();
+        else if (tmp != "..") stk.push_back(tmp);
+    }
+    for(auto str : stk) res += "/"+str;
+    return res.empty() ? "/" : res;
+}
+};

81.Search in a rotated sorted array II.java

@@ -0,0 +1,31 @@
+  public boolean search(int[] nums, int target) {
+        int start = 0, end = nums.length - 1, mid = -1;
+        while(start <= end) {
+            mid = (start + end) / 2;
+            if (nums[mid] == target) {
+                return true;
+            }
+            //If we know for sure right side is sorted or left side is unsorted
+            if (nums[mid] < nums[end] || nums[mid] < nums[start]) {
+                if (target > nums[mid] && target <= nums[end]) {
+                    start = mid + 1;
+                } else {
+                    end = mid - 1;
+                }
+            //If we know for sure left side is sorted or right side is unsorted
+            } else if (nums[mid] > nums[start] || nums[mid] > nums[end]) {
+                if (target < nums[mid] && target >= nums[start]) {
+                    end = mid - 1;
+                } else {
+                    start = mid + 1;
+                }
+            //If we get here, that means nums[start] == nums[mid] == nums[end], then shifting out
+            //any of the two sides won't change the result but can help remove duplicate from
+            //consideration, here we just use end-- but left++ works too
+            } else {
+                end--;
+            }
+        }
+        
+        return false;
+    }