Merge pull request #12 from thekalyan001/main

Leet code problem First Missing Positive added

Author: gantavyamalviya

CPP/Leetcode-First Missing Positive.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+ int firstMissingPositive(vector<int>& nums) {
+ int n=nums.size();
+ 
+ //number should be always between 1 to n
+ for(int i=0;i<n;i++){
+ if(nums[i]<=0 or nums[i]>n)
+ nums[i]=n+1;
+ }
+ 
+ //
+ for(int i=0;i<n;i++){
+ if(abs(nums[i])<=n){
+ int index=abs(nums[i])-1;
+ nums[index]=-abs(nums[index]);
+ }
+ }
+ for(int i=0;i<n;i++){
+ if(nums[i]>0)return i+1;
+ }
+ return n+1;
+ }
+};