diff --git a/221. Maximal Square.cpp b/221. Maximal Square.cpp
new file mode 100644
index 0000000..29441fb
--- /dev/null
+++ b/221. Maximal Square.cpp	
@@ -0,0 +1,57 @@
+class Solution {
+public:
+    int maximalSquare(vector<vector<char>> matrix) 
+    {
+        int n=matrix.size();
+        int m=matrix[0].size();
+        int top[n][m];
+        for(int i=0;i<m;i++)
+        {
+            top[0][i]=matrix[0][i]-'0';
+        }
+        for(int i=1;i<n;i++)
+        {
+            for(int j=0;j<m;j++)
+            {
+                if(matrix[i][j]=='0')
+                {
+                    top[i][j]=0;
+                }
+                else
+                {
+                    top[i][j]=1+top[i-1][j];
+                }
+            }
+        }
+        for(int i=0;i<n;i++)
+        {
+            for(int j=1;j<m;j++)
+            {
+                
+                top[i][j]+=top[i][j-1];
+            }
+        }
+        
+        int ans=0;
+        for(int i=0;i<n;i++)
+        {
+            for(int j=0;j<m;j++)
+            {
+                for(int k=1;k<=min(i+1,j+1);k++)
+                {
+                    int r=0;
+                    r+=top[i][j];
+                    if(i-k>=0)
+                        r-=top[i-k][j];
+                    if(j-k>=0)
+                        r-=top[i][j-k];
+                    if(j-k>=0&&i-k>=0)
+                        r+=top[i-k][j-k];
+                    if(r==k*k)
+                    ans=max(ans,k*k);
+                }
+            }
+        }
+        return ans;
+    }
+};