in place quicksort

in-place quicksort.txt

@@ -0,0 +1,59 @@
+// in-place quicksort... also called  Lomuto Partitioning method.
+// here the last element is taken as the pivot element 
+// also, in the output, the array is printed after every successful partition 
+
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+#include <stdlib.h>
+
+void display(int n, int *a)
+    {
+    for(int i=0;i<n;i++)
+        printf("%d ",a[i]);
+    printf("\n");
+}
+int partition(int p,int q,int n,int *a)
+    {
+    int x=a[q],temp;
+    int i=p,j=p;
+    while(j<q)
+        {
+        if(a[j]<x)
+            {
+            temp=a[i];
+            a[i]=a[j];
+            a[j]=temp;
+            i++;
+        }
+        j++;
+    }
+    temp=a[q];
+    a[q]=a[i];
+    a[i]=temp; 
+    return i;
+}
+void quicksort(int p,int q, int n,int *a) {
+   if(p>=q)
+       return;
+    else
+        {
+        int m;
+        m=partition(p,q,n,a);
+        display(n,a);
+        quicksort(p,m-1,n,a);
+        quicksort(m+1,q,n,a);
+    }
+}
+int main(void) {
+   int ar_size;
+   scanf("%d", &ar_size);
+   int ar[ar_size], i;
+   for(i = 0; i < ar_size; i++) { 
+      scanf("%d", &ar[i]); 
+   }
+
+   quicksort(0,ar_size-1,ar_size, ar);
+
+   return 0;
+}

number_of_islands.cpp

@@ -0,0 +1,40 @@
+// https://leetcode.com/problems/number-of-islands/
+// Approach to solution - DFS
+
+class Solution {
+public:
+    void topol(vector<vector<char>>& grid, int i , int j, int &width, int &len) {
+        grid[i][j] = '0';
+
+        if(i!=0 && '0' != grid[i-1][j]) {
+            topol(grid, i-1, j, width, len);
+        }
+        if(j!=0 && '0' != grid[i][j-1]) {
+            topol(grid, i, j-1, width, len);
+        }
+        if(i!=len-1 && '0' != grid[i+1][j]) {
+            topol(grid, i+1, j, width, len);
+        }
+        if(j!=width-1 && '0' != grid[i][j+1]) {
+            topol(grid, i, j+1, width, len);
+        }
+    }
+
+    int numIslands(vector<vector<char>>& grid) {
+        if(grid.empty()) {
+            return 0;
+        }
+        int count = 0, len = grid.size(), width = grid[0].size();
+        //cout << len << " " << width << endl;
+        unordered_map<int , bool> visited;
+        for(int i = 0 ; i < len ; ++i) {
+            for(int j = 0 ; j < width ; ++j) {
+                if('0' != grid[i][j]) {
+                    topol(grid, i, j, width, len);
+                    ++count;
+                }
+            }
+        }
+        return count;
+    }
+};