diff --git a/C/lcs.c b/C/lcs.c
new file mode 100644
index 0000000..459579c
--- /dev/null
+++ b/C/lcs.c
@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <string.h>
+
+int main()
+{
+    int j;
+    char str1[50], str2[50];
+    scanf("%s %s", str1, str2);
+    
+    int len1, len2;
+    len1=strlen(str1) + 1;
+    len2=strlen(str2) + 1;
+    
+    int lcs[len1][len2];
+    
+    for (int i=0;i<len1;i++)
+    {
+        for(j=0;j<len2;j++)
+        {
+            if(i==0 || j==0)
+            {
+                lcs[i][j]=0;
+            }
+            else
+            {
+                if(str1[i-1]==str2[j-1])
+                {
+                    lcs[i][j]= 1+lcs[i-1][j-1];
+                }
+                else if(lcs[i-1][j]>lcs[i][j-1])
+                {
+                    lcs[i][j]=lcs[i-1][j];
+                }
+                else
+                {
+                    lcs[i][j]=lcs[i][j-1];
+                }
+            }
+        }
+    }
+    
+    if (len1<len2 && (len1-1==lcs[len1-1][j-1]))
+    {
+        printf("YES");
+    }
+    else
+    {
+        printf("NO");
+    }
+    
+    return 0;
+}
\ No newline at end of file
diff --git a/C/strassen.c b/C/strassen.c
new file mode 100644
index 0000000..435a148
--- /dev/null
+++ b/C/strassen.c
@@ -0,0 +1,141 @@
+#include <stdio.h>
+
+void Strassen(int n, int (*P)[n],int (*Q)[n], int (*R)[n] )
+{
+    if (n==1)
+    {
+        R[0][0]=P[0][0]*Q[0][0];
+    }
+    else 
+    {
+        int a[n/2][n/2], b[n/2][n/2], c[n/2][n/2], d[n/2][n/2];
+        int e[n/2][n/2], f[n/2][n/2], g[n/2][n/2], h[n/2][n/2];
+        int p1[n/2][n/2], p2[n/2][n/2], p3[n/2][n/2], p4[n/2][n/2], p5[n/2][n/2], p6[n/2][n/2], p7[n/2][n/2];
+        int C1[n/2][n/2], C2[n/2][n/2], C3[n/2][n/2], C4[n/2][n/2];
+        
+        int t1[n/2][n/2], t2[n/2][n/2], t3[n/2][n/2], t4[n/2][n/2], t5[n/2][n/2];
+        int t6[n/2][n/2], t7[n/2][n/2], t8[n/2][n/2], t9[n/2][n/2], t10[n/2][n/2];
+        
+        for (int i=0;i<n/2;i++)
+        {
+            for (int j=0;j<n/2;j++)
+            {
+                a[i][j] = P[i][j];
+                b[i][j] = P[i][n/2 + j];
+                c[i][j] = P[n/2+i][j];
+                d[i][j] = P[n/2+i][n/2+j];
+                
+                e[i][j] = Q[i][j];
+                f[i][j] = Q[i][n/2 + j];
+                g[i][j] = Q[n/2+i][j];
+                h[i][j] = Q[n/2+i][n/2+j];
+            }
+        }
+        
+        for (int i=0;i<n/2;i++)
+        {
+            for (int j=0;j<n/2;j++)
+            {
+                t1[i][j] = f[i][j] - h[i][j];
+                t2[i][j] = a[i][j] + b[i][j];
+                t3[i][j] = c[i][j] + d[i][j];
+                t4[i][j] = g[i][j] - e[i][j];
+                t5[i][j] = a[i][j] + d[i][j];
+                t6[i][j] = e[i][j] + h[i][j];
+                t7[i][j] = b[i][j] - d[i][j];
+                t8[i][j] = g[i][j] + h[i][j];
+                t9[i][j] = a[i][j] - c[i][j];
+                t10[i][j] = e[i][j] + f[i][j];
+                         
+                
+            }
+        }
+        
+        Strassen(n/2,a,t1,p1);
+        Strassen(n/2,t2,h,p2);
+        Strassen(n/2,t3,e,p3);
+        Strassen(n/2,d,t4,p4);
+        Strassen(n/2,t5,t6,p5);
+        Strassen(n/2,t7,t8,p6);
+        Strassen(n/2,t9,t10,p7);
+        
+        for (int i=0;i<n/2;i++)
+        {
+            for (int j=0;j<n/2;j++)
+            {
+                C1[i][j] = p5[i][j] + p4[i][j] - p2[i][j] + p6[i][j];
+                C2[i][j] = p1[i][j] + p2[i][j];
+                C3[i][j] = p3[i][j] + p4[i][j];
+                C4[i][j] = p1[i][j] + p5[i][j] - p3[i][j] - p7[i][j];
+            }
+        }
+        
+        for (int i=0;i<n;i++)
+        {
+            for(int j=0;j<n;j++)
+            {
+                if(i<n/2 && j<n/2)
+                {
+                    R[i][j] = C1[i][j];
+                }
+                if(i<n/2 && j>=n/2)
+                {
+                    R[i][j] = C2[i][j - n/2];
+                }
+                if(i>=n/2 && j<n/2)
+                {
+                    R[i][j] = C3[i - n/2][j];
+                }
+                if(i>=n/2 && j>=n/2)
+                {
+                    R[i][j] = C4[i - n/2][j - n/2];
+                }
+                
+            }
+        }
+    }
+}
+
+int main()
+{
+    int n,i,j;
+    scanf("%d",&n);
+    
+    int P[n][n], Q[n][n], R[n][n];
+    for (i=0;i<n;i++)
+    {
+        for(j=0;j<n;j++)
+        {
+            scanf("%d",&P[i][j]);
+        }
+    }
+    
+    for (i=0;i<n;i++)
+    {
+        for(j=0;j<n;j++)
+        {
+            scanf("%d",&Q[i][j]);
+        }
+    }
+    
+    for (i=0;i<n;i++)
+    {
+        for(j=0;j<n;j++)
+        {
+            scanf("%d",&R[i][j]);
+        }
+    }
+    
+    Strassen(n,P,Q,R);
+    
+    for(i=0;i<n;i++)
+    {
+        for(j=0;j<n;j++)
+        {
+            printf("%d\n", R[i][j]);
+        }
+    }
+    
+    return 0;
+    
+}
\ No newline at end of file
diff --git a/python/n_queens.py b/python/n_queens.py
new file mode 100644
index 0000000..85fbc49
--- /dev/null
+++ b/python/n_queens.py
@@ -0,0 +1,56 @@
+def initialise(n):
+    for key in ['queen','row','col','nw','sw']:
+        board[key] = {}
+    for i in range(n):
+        board['queen'][i] = -1
+        board['row'][i] = 0
+        board['col'][i] = 0
+    
+    for i in range(-(n-1),n):
+        board['nw'][i] = 0;
+        board['sw'][i+n-1] = 0;
+        
+def free(i,j):
+    if(board['row'][i]==0 and board['col'][j]==0 and board['nw'][j-i]==0 and board['sw'][j+i]==0):
+        return True
+    return False
+        
+def addQueen(i,j):
+    board['queen'][i] = j
+    board['row'][i] = 1
+    board['col'][j] = 1
+    board['nw'][j-i] = 1
+    board['sw'][j+i] = 1
+    
+def undoQueen(i,j):
+    board['queen'][i] = -1
+    board['row'][i] = 0
+    board['col'][j] = 0
+    board['nw'][j-i] = 0
+    board['sw'][j+i] = 0
+    
+def placeQueen(i):
+    n = len(board['queen'].keys())
+    for j in range(n):
+        if(free(i,j)):
+            addQueen(i,j)
+            if i==n-1:
+                return True
+            else:
+                extendSoln = placeQueen(i+1)
+            
+            if(extendSoln):
+                return True
+            else:
+                undoQueen(i,j)
+    else:
+        return False
+        
+board = {}
+n = int(input())
+initialise(n)
+
+if(placeQueen(0)):
+    for row in board['queen'].keys():
+        print((row, board['queen'][row]))
+        
\ No newline at end of file