From 24c9ea91924a024321b752d54169d992057e0dcd Mon Sep 17 00:00:00 2001
From: Debashis Nandi <debashisnandi576@gmail.com>
Date: Fri, 5 Jun 2026 01:15:24 +0530
Subject: [PATCH] feat: POTD 2026-06-04 solved

---
 src/3600-3699/3635.cpp   |   2 +-
 src/3700-3799/3751.cpp   | 154 +++++++++++++++++++++++++++++++++++++++
 tests/3700-3799/3751.txt |  20 +++++
 3 files changed, 175 insertions(+), 1 deletion(-)
 create mode 100644 src/3700-3799/3751.cpp
 create mode 100644 tests/3700-3799/3751.txt

diff --git a/src/3600-3699/3635.cpp b/src/3600-3699/3635.cpp
index 355430a..862dff7 100644
--- a/src/3600-3699/3635.cpp
+++ b/src/3600-3699/3635.cpp
@@ -6,7 +6,7 @@ array, greedy
 
 Problem Description
 
-3635. Earliest Finish Time for Land and Water Rides I
+3635. Earliest Finish Time for Land and Water Rides II
 
 You are given two categories of theme park attractions: land rides and water rides.
 Land rides
diff --git a/src/3700-3799/3751.cpp b/src/3700-3799/3751.cpp
new file mode 100644
index 0000000..8449825
--- /dev/null
+++ b/src/3700-3799/3751.cpp
@@ -0,0 +1,154 @@
+/*
+Tags
+level-medium
+dp, digit-dp, math
+
+
+Problem Description
+3751. Total Waviness of Numbers in Range I
+You are given two integers num1 and num2 representing an inclusive range [num1, num2].
+The waviness of a number is defined as the total count of its peaks and valleys:
+A digit is a peak if it is strictly greater than both of its immediate neighbors.
+A digit is a valley if it is strictly less than both of its immediate neighbors.
+The first and last digits of a number cannot be peaks or valleys.
+Any number with fewer than 3 digits has a waviness of 0.
+Return the total sum of waviness for all numbers in the range [num1, num2].
+
+Example 1:
+Input: num1 = 120, num2 = 130
+Output: 3
+Explanation:
+In the range [120, 130]:
+120: middle digit 2 is a peak, waviness = 1.
+121: middle digit 2 is a peak, waviness = 1.
+130: middle digit 3 is a peak, waviness = 1.
+All other numbers in the range have a waviness of 0.
+Thus, total waviness is 1 + 1 + 1 = 3.
+
+Example 2:
+Input: num1 = 198, num2 = 202
+Output: 3
+Explanation:
+In the range [198, 202]:
+198: middle digit 9 is a peak, waviness = 1.
+201: middle digit 0 is a valley, waviness = 1.
+202: middle digit 0 is a valley, waviness = 1.
+All other numbers in the range have a waviness of 0.
+Thus, total waviness is 1 + 1 + 1 = 3.
+
+Example 3:
+Input: num1 = 4848, num2 = 4848
+Output: 2
+Explanation:
+Number 4848: the second digit 8 is a peak, and the third digit 4 is a valley, giving a waviness of 2.
+
+Constraints:
+1 <= num1 <= num2 <= 10^5
+*/
+
+#include <iostream>
+#include <vector>
+#include <string>
+#include <algorithm>
+#include <numeric>
+#include <cmath>
+#include <queue>
+#include <stack>
+#include <set>
+#include <map>
+#include <unordered_map>
+#include <unordered_set>
+#include <sstream>
+#include <limits>
+#include <iomanip>
+#include <functional>
+#include <cstring>
+#include <climits>
+#include "../../core/core.h"
+using namespace std;
+
+using ll = long long;
+class Solution {
+private:
+	ll memoCount[16][10][10];
+	ll memoSum[16][10][10];
+	string s;
+public:
+	pair<ll, ll> dfs(int pos, int prev, int cur, bool isLimit, bool isLeading)
+	{
+		if (pos == s.length())
+		{
+			return { 1,0 };
+		}
+
+		if (!isLimit && !isLeading && prev >= 0 && cur >= 0)
+		{
+			if (memoCount[pos][prev][cur] != -1)
+			{
+				return { memoCount[pos][prev][cur], memoSum[pos][prev][cur] };
+			}
+		}
+
+		ll count = 0;
+		ll sum = 0;
+		int limitDigit = isLimit ? (s[pos] - '0') : 9;
+		for (int digit = 0; digit <= limitDigit; digit++)
+		{
+			bool nextLeading = isLeading && (digit == 0);
+			int nextPrev = cur;
+			int nextCur = nextLeading ? -1 : digit;
+			bool nextLimit = isLimit && (digit == limitDigit);
+
+			pair<ll, ll>result = this->dfs(pos + 1, nextPrev, nextCur, nextLimit, nextLeading);
+			ll subCount = result.first;
+			ll subSum = result.second;
+
+			if (!nextLeading && prev >= 0 && cur >= 0)
+			{
+				bool isPeak = (prev<cur && cur>digit);
+				bool isTrough = (prev > cur && cur < digit);
+
+				if (isPeak || isTrough)
+				{
+					sum += subCount;
+				}
+			}
+
+			count += subCount;
+			sum += subSum;
+		}
+
+		if (!isLimit && !isLeading && prev >= 0 && cur >= 0)
+		{
+			memoCount[pos][prev][cur] = count;
+			memoSum[pos][prev][cur] = sum;
+		}
+
+		return { count, sum };
+	}
+	ll solve(int num)
+	{
+		if (num < 100)
+		{
+			return 0;
+		}
+		s = to_string(num);
+		memset(memoCount, -1, sizeof(memoCount));
+		memset(memoSum, -1, sizeof(memoSum));
+		pair<ll, ll> result = this->dfs(0, -1, -1, true, true);
+		return result.second;
+	}
+	int totalWaviness(int num1, int num2) {
+		return (int)(this->solve(num2) - this->solve(num1 - 1));
+	}
+};
+
+int main()
+{
+	int num1, num2;
+	cin >> num1 >> num2;
+	Solution sol;
+	int result = sol.totalWaviness(num1, num2);
+	cout << result << "\n";
+	return 0;
+}
\ No newline at end of file
diff --git a/tests/3700-3799/3751.txt b/tests/3700-3799/3751.txt
new file mode 100644
index 0000000..4451c12
--- /dev/null
+++ b/tests/3700-3799/3751.txt
@@ -0,0 +1,20 @@
+Test Case 1:
+Input:
+120
+130
+Output:
+3
+
+Test Case 2:
+Input:
+198
+202
+Output:
+3
+
+Test Case 3:
+Input:
+4848
+4848
+Output:
+2
\ No newline at end of file