solved: 41. First Missing Positive

Signed-off-by: rajput-hemant <rajput.hemant2001@gmail.com>

Author: rajput-hemant

src/0001-0100/041 - First Missing Positive/first_missing_positive.rs

@@ -0,0 +1,26 @@
+impl Solution {
+    pub fn first_missing_positive(nums: Vec<i32>) -> i32 {
+        let (mut nums, mut i) = (nums, 0);
+
+        while i < nums.len() {
+            let num = nums[i];
+
+            // if the number is in the range [1, nums.len()] and not in the right position
+            // swap it with the number at the right position
+            if num > 0 && num <= nums.len() as i32 && num != nums[num as usize - 1] {
+                nums.swap(i, num as usize - 1);
+            } else {
+                i += 1;
+            }
+        }
+
+        // find the first missing positive number
+        for (i, num) in nums.iter().enumerate() {
+            if num != &(i as i32 + 1) {
+                return i as i32 + 1;
+            }
+        }
+
+        nums.len() as i32 + 1
+    }
+}