solve 41

Author: Zhang Xiaodong

src/solution/mod.rs

@@ -36,3 +36,4 @@ mod s0037_sudoku_solver;
 mod s0038_count_and_say;
 mod s0039_combination_sum;
 mod s0040_combination_sum_ii;
+mod s0041_first_missing_positive;

src/solution/s0041_first_missing_positive.rs

@@ -0,0 +1,69 @@
+/**
+ * [41] 缺失的第一个正数
+ *
+ * 给你一个未排序的整数数组 nums ，请你找出其中没有出现的最小的正整数。
+ * 请你实现时间复杂度为 O(n) 并且只使用常数级别额外空间的解决方案。
+ *  
+ * 示例 1：
+ * 
+ * 输入：nums = [1,2,0]
+ * 输出：3
+ * 
+ * 示例 2：
+ * 
+ * 输入：nums = [3,4,-1,1]
+ * 输出：2
+ * 
+ * 示例 3：
+ * 
+ * 输入：nums = [7,8,9,11,12]
+ * 输出：1
+ * 
+ *  
+ * 提示：
+ * 
+ * 	1 <= nums.length <= 5 * 10^5
+ * 	-2^31 <= nums[i] <= 2^31 - 1
+ * 
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.cn/problems/first-missing-positive/
+// discuss: https://leetcode.cn/problems/first-missing-positive/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn first_missing_positive(nums: Vec<i32>) -> i32 {
+        let mut nums: Vec<i32> = nums;
+        for i in 0..nums.len() {
+            if nums[i] <= 0 || nums[i] >= nums.len() as i32 {
+                continue;
+            }
+            if (i+1) as i32 != nums[i] {
+                let j = (nums[i] - 1) as usize;
+                nums.swap(i, j);
+            }
+        }
+        for i in 0..nums.len() {
+            if (i+1) as i32 != nums[i] {
+                return (i+1) as i32;
+            }
+        }
+        nums.len() as i32
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_41() {
+        assert_eq!(
+            Solution::first_missing_positive(vec![8,2,3,1,8,1,2,8]),4
+        )
+    }
+}