modified first_missing_number and balanced paranthesis

Author: smv1999

Arrays/first_missing_positive.cpp

@@ -1,5 +1,5 @@
 /*
-Given an array of integers, find the first missing positive integer in linear time and constant space. In other words, 
+Given an array of integers, find the first missing positive integer in linear time and constant space. In other words,
 find the lowest positive integer that does not exist in the array. The array can contain duplicates and negative numbers as well.
 
 For example, the input [3, 4, -1, 1] should give 2. The input [1, 2, 0] should give 3.
@@ -26,7 +26,7 @@ int firstMissingNumber(int arr[], int n)
     int index, temp;
     for(index=0;index<n;index++)
     {
-        while(arr[index]!=arr[arr[index]-1] && arr[index]>=1 && arr[index]<=n)
+        while(arr[index]>=1 && arr[index]<=n && arr[index]!=arr[arr[index]-1])
         {
             temp = arr[arr[index]-1];
             arr[arr[index]-1] = arr[index];

Data Structures/Stack/BalancedParantheses.cpp

@@ -1,59 +1,39 @@
-// Given a string of parantheses, braces and square brackets. We need to check whether they are balanced.
-
-#include<iostream>
-#include<stack>
-#include<algorithm>
-
+#include <bits/stdc++.h>
 using namespace std;
+bool isBalanced(string);
 
-bool isbalanced(string s)
-{  stack<char> st;
-    char x;
+bool isBalanced(string expr)
+{
+    stack<int> st;
+    int size = expr.length();
 
-    for(int i=0;i<s.length();i++)
+    for(int i=0;i<size;i++)
     {
-        if(s[i]=='(' || s[i]=='{' || s[i]=='[')
-        {
-            st.push(s[i]);
-            continue;
+        if(expr[i] == '(' || expr[i] == '[' || expr[i] == '{'){
+            st.push(expr[i]);
         }
-         if (s.empty()) 
-         {
-           return false;
-         }
-           
-        switch (s[i])
-        {
-        case ')':
-            x = st.top();
-            st.pop();
-            if(s[i]=='{' || s[i]=='[')
-                return false;
-            break;
-        case '}':
-            x = st.top();
-            st.pop();
-            if(s[i]=='(' || s[i]=='[')
-                return false;
-            break;
-        case ']':
-            x = st.top();
+        else if(!st.empty() && ((st.top()=='(' && expr[i]==')') ||
+        (st.top()=='[' && expr[i]==']') || (st.top()=='{' && expr[i]=='}'))){
+
             st.pop();
-            if(s[i]=='(' || s[i]=='{')
-                return false;
-            break;
         }
+        else return false;
     }
-     return st.empty();
 
+    return st.empty();
 }
 
-int main(int argc, char const *argv[])
-{
-    string s;
-    cin>>s;
-    
-    cout<<(isbalanced(s) ? "Yes" : "No");
-    
-    return 0;
+int main() {
+	//code
+	int t;
+	string expr;
+	cin>>t;
+	while(t--)
+	{
+	    cin>>expr;
+	    if(isBalanced(expr))
+	        cout<<"balanced\n";
+	    else cout<<"not balanced\n";
+	}
+	return 0;
 }