From 9238af57e834011dd2a8741be2530cf5dd177f74 Mon Sep 17 00:00:00 2001
From: jackfiled <xcrenchangjun@outlook.com>
Date: Thu, 28 Nov 2024 12:01:08 +0800
Subject: [PATCH] 20241128 finished.

---
 src/problem/mod.rs                            |  2 +
 ...250_find_the_count_of_monotonic_pairs_i.rs | 47 +++++++++++++++++++
 2 files changed, 49 insertions(+)
 create mode 100644 src/problem/p3250_find_the_count_of_monotonic_pairs_i.rs

diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 4540b78..ff935a0 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -340,3 +340,5 @@ mod p632_smallest_range_covering_elements_from_k_lists;
 mod p3206_alternating_groups_i;
 
 mod p3208_alternating_groups_ii;
+
+mod p3250_find_the_count_of_monotonic_pairs_i;
diff --git a/src/problem/p3250_find_the_count_of_monotonic_pairs_i.rs b/src/problem/p3250_find_the_count_of_monotonic_pairs_i.rs
new file mode 100644
index 0000000..b55225b
--- /dev/null
+++ b/src/problem/p3250_find_the_count_of_monotonic_pairs_i.rs
@@ -0,0 +1,47 @@
+/**
+ * [3250] Find the Count of Monotonic Pairs I
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+const MOD: i32 = 1_000_000_007;
+
+impl Solution {
+    pub fn count_of_pairs(nums: Vec<i32>) -> i32 {
+        let n = nums.len();
+        let nums: Vec<usize> = nums.into_iter().map(|x| x as usize).collect();
+        let max_num = *nums.iter().max().unwrap();
+
+        let mut dp = vec![vec![0; max_num + 1]; n];
+
+        for i in 0..=nums[0] {
+            dp[0][i] = 1;
+        }
+
+        for i in 1..n {
+            for v2 in 0..=nums[i] {
+                for v1 in 0..=v2 {
+                    if nums[i - 1] >= v1 && nums[i - 1] - v1 >= nums[i] - v2 {
+                        dp[i][v2] = (dp[i][v2] + dp[i - 1][v1]) % MOD;
+                    }
+                }
+            }
+        }
+
+        dp[n - 1].iter().fold(0, |acc, e| (acc + *e) % MOD)
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_3250() {
+        assert_eq!(4, Solution::count_of_pairs(vec![2, 3, 2]));
+        assert_eq!(126, Solution::count_of_pairs(vec![5, 5, 5, 5]));
+    }
+}