parenthesis checker using stack

parenthesis checker

@@ -0,0 +1,61 @@
+#include<iostream>
+using namespace std;
+#include<string.h>
+#define n 20
+char push(char);
+char pop();
+int top=-1;
+int stack[20];
+main()
+{
+  char s[20],temp;
+  cout<<"enter expression"<<endl;
+  cin>>s;
+  int x=1,i;
+  for(i=0;i<strlen(s);i++)
+  {
+  	if(s[i]=='('||s[i]=='{'||s[i]=='[')
+  	push(s[i]);
+  	if(s[i]==')'||s[i]=='}'||s[i]==']')
+  	{
+  		if(top==-1)
+  		x=0;
+  		else
+  		{
+  			temp=pop();
+  			if(s[i]==')'&&(temp=='{'||temp=='['))
+  			x=0;
+  			if(s[i]=='}'&&(temp=='('||temp=='['))
+  			x=0;
+  			if(s[i]==']'&&(temp=='{'||temp=='('))
+  			x=0;
+		  }
+	  }
+
+	  }
+	  if(top>=0)
+	  x=0;
+	  if(x==0)
+	  cout<<"invalid\n";
+	  else
+	  cout<<"valid\n";	
+}
+char push(char a)
+{
+	if(top==n-1)
+	cout<<"stack overflow"<<endl;
+	else
+	{
+		top++;
+		stack[top]=a;
+	}
+}
+char pop()
+{
+	if(top==-1)
+	cout<<"stack underflow"<<endl;
+	else
+	{
+		return(stack[top--]);
+	}
+}

transitive closure

@@ -0,0 +1,45 @@
+#include<stdio.h>
+#include<conio.h>
+#include<iostream>
+using namespace std;
+void printSolution(int reach[][4])
+{
+   cout<<"Following matrix is transitive closure of the given graph\n";
+    for (int i = 0; i < 4; i++)
+    {
+       for (int j = 0; j < 4; j++)
+       {
+	     cout<<reach[i][j]<<" ";
+       }
+        cout<<endl;
+ }
+}
+void transitiveClosure(int graph[][4])
+{
+    int reach[4][4], i, j, k;
+    for (i = 0; i < 4; i++)
+    {
+      for (j = 0; j < 4; j++)
+	  {
+         reach[i][j] = graph[i][j];
+		 }
+}
+    for (k = 0; k < 4; k++)
+    {
+       for (i = 0; i < 4; i++)
+       {
+	      for (j = 0; j < 4; j++)
+            {
+		    	reach[i][j] = reach[i][j] || (reach[i][k] && reach[k][j]);
+            }
+        }
+    }
+    printSolution(reach);
+}
+int main()
+{
+   int graph[4][4] = { {1, 1, 0, 1},{0, 1, 1, 0},{0, 0, 1, 1},{0, 0, 0, 1}};
+
+            transitiveClosure(graph);
+			getch();
+}