From 82961900b5fc6da114de7e6784bd64ce771ec302 Mon Sep 17 00:00:00 2001
From: urvashigupta7 <urvashi072000@gmail.com>
Date: Sat, 3 Oct 2020 09:14:02 +0530
Subject: [PATCH] first-missing-positive

---
 FirstMissingPositive.java | 41 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 FirstMissingPositive.java

diff --git a/FirstMissingPositive.java b/FirstMissingPositive.java
new file mode 100644
index 0000000..6107004
--- /dev/null
+++ b/FirstMissingPositive.java
@@ -0,0 +1,41 @@
+
+import java.util.ArrayList;
+import java.util.List;
+
+class Solution {
+    public static void main(String []args){
+     int []nums={1,2,0};
+     int target=7;
+        System.out.println(firstMissingPositive(nums));
+    }
+    public static int firstMissingPositive(int[] nums) {
+        int size=segregate(nums);
+        if(size==0){
+            return 1;
+        }
+        for(int i=0;i<size;i++){
+            int abs=Math.abs(nums[i]);
+            if(abs-1>=0&&abs-1<size&&nums[abs-1]>0){
+                nums[abs-1]=-nums[abs-1];
+            }
+        }
+        for(int i=0;i<size;i++){
+            if(nums[i]>0){
+                return i+1;
+            }
+        }
+        return size+1;
+    }
+    public static int segregate(int []nums){
+        int start=-1;
+        for(int i=0;i<nums.length;i++){
+            if(nums[i]>0){
+                start++;
+                int temp=nums[i];
+                nums[i]=nums[start];
+                nums[start]=temp;
+            }
+        }
+        return start+1;
+    }
+}
\ No newline at end of file