From 07d0d492e13505107755d5781cc0e6289ff77151 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Khoa=20Hu=E1=BB=B3nh=20=28Daniel=29?= <khoa0319@gmail.com>
Date: Tue, 26 Mar 2024 23:47:29 +0700
Subject: [PATCH] Create main.go

---
 solution/41/main.go | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 solution/41/main.go

diff --git a/solution/41/main.go b/solution/41/main.go
new file mode 100644
index 0000000..cacd079
--- /dev/null
+++ b/solution/41/main.go
@@ -0,0 +1,36 @@
+package main
+
+func firstMissingPositive(nums []int) int {
+    n := len(nums)
+
+	for i := 0; i < n; i++ {
+		if nums[i] <= 0 || nums[i] > n {
+			nums[i] = n + 1
+		}
+	}
+
+	for i := 0; i < n; i++ {
+		val := abs(nums[i])
+		if val >= 1 && val <= n {
+			flagIndex := val - 1
+			if nums[flagIndex] > 0 {
+				nums[flagIndex] *= -1
+			}
+		}
+	}
+
+	for i := 1; i <= n; i++ {
+		if nums[i - 1] > 0 {
+			return i
+		}
+	}
+
+	return n + 1
+}
+
+func abs(x int) int {
+    if x < 0 {
+        return -x
+    }
+    return x
+}