From 70cfb1c87f809e4d106d74a9726e9192c700f962 Mon Sep 17 00:00:00 2001
From: colorbox <colorbox222@gmail.com>
Date: Mon, 4 Aug 2025 01:20:29 +0900
Subject: [PATCH] 276. Paint Fence

---
 276/step1.cpp | 35 +++++++++++++++++++++++++++++++++++
 276/step2.cpp | 24 ++++++++++++++++++++++++
 276/step3.cpp | 20 ++++++++++++++++++++
 3 files changed, 79 insertions(+)
 create mode 100644 276/step1.cpp
 create mode 100644 276/step2.cpp
 create mode 100644 276/step3.cpp

diff --git a/276/step1.cpp b/276/step1.cpp
new file mode 100644
index 0000000..1823045
--- /dev/null
+++ b/276/step1.cpp
@@ -0,0 +1,35 @@
+/*
+
+Solve Time: 20:00
+
+Time: O(n)
+Space: O(n)
+
+色の数で混乱しかけたが
+- 前に使った色と同じ色でなければよいので、色の数の多さはそこまで影響がない
+- 1枚塗るか2枚塗るというのを配列を1,2進むで表現可能
+の二点に気づいたら割とすんなりできた
+kを入れる位置に少し悩んだが、なんとかパスした
+*/
+
+class Solution {
+public:
+  int numWays(int n, int k) {
+    if (k == 1 && n >= 3) { 
+      return 0;
+    }
+    if (n == 1 || k == 1) {
+      return k;
+    }
+    vector<long> dp(n + 1);
+    dp[1] = k;
+    dp[2] = k;
+    for (int i = 2; i <= n; ++i) {
+      dp[i] += dp[i - 1] * (k - 1);
+      if (i >= 2) {
+        dp[i] += dp[i - 2] * (k - 1);
+      }
+    }
+    return dp[n];
+  }
+};
diff --git a/276/step2.cpp b/276/step2.cpp
new file mode 100644
index 0000000..856d599
--- /dev/null
+++ b/276/step2.cpp
@@ -0,0 +1,24 @@
+class Solution {
+public:
+  int numWays(int n, int k) {
+    if (k == 1) {
+      if (n>=3) {
+        return 0;
+      }
+      return 1;
+    }
+    if (n == 1) {
+      return k;
+    }
+    vector<long> dp(n+1);
+    dp[1] = k;
+    dp[2] = k;
+    for (int i = 2; i <= n; ++i) {
+      dp[i] += dp[i - 1] * (k - 1);
+      if (i > 2) {
+        dp[i] += dp[i - 2] * (k - 1);
+      }
+    }
+    return dp[n];
+  }
+};
diff --git a/276/step3.cpp b/276/step3.cpp
new file mode 100644
index 0000000..f890352
--- /dev/null
+++ b/276/step3.cpp
@@ -0,0 +1,20 @@
+class Solution {
+public:
+  int numWays(int n, int k) {
+    if (n == 1) {
+      return k;
+    }
+    if (n == 2) {
+      return k * (k - 1) + k;
+    }
+
+    int previous_count = k;
+    int count = k * (k - 1) + k;
+    for (int i = 2; i < n; ++i) {
+      int tmp = count;
+      count = count * (k - 1) + previous_count * (k - 1);
+      previous_count = tmp;
+    }
+    return count;
+  }
+};