Sep2: daily update, Sliding window [M]

impl of sliding window, Time: O(N), Space: O(1)

try to familize the bit operation, bit operation is fast, which is
widely used in hardware programming.

daily/Aug31.cc

@@ -0,0 +1,79 @@
+#include <iostream>
+using namespace std;
+
+class Solution {
+ public:
+  bool canMakeSquare(vector<vector<char>>& grid) {
+    /**
+    *  B B B .  B w b
+    *  w w w .  w b w
+    *  b b b    b w b   b
+    */
+    int cnt_w = 0;
+    for (int i = 0; i < 2; i++) {
+      for (int j = 0; j < 2; j++) {
+        if (grid[i][j] == 'W') {
+          cnt_w ++;
+        }
+      }
+    }
+    if (cnt_w != 2) return true;
+    cnt_w = 0;
+
+    for (int i = 0; i < 2; i++) {
+      for (int j = 1; j < 3; j++) {
+        if (grid[i][j] == 'W') {
+          cnt_w ++;
+        }
+      }
+    }
+    if (cnt_w != 2) return true;
+    cnt_w = 0;
+
+    for (int i = 1; i < 3; i++) {
+      for (int j = 0; j < 2; j++) {
+        if (grid[i][j] == 'W') {
+          cnt_w ++;
+        }
+      }
+    }
+    if (cnt_w != 2) return true;
+    cnt_w = 0;
+
+    for (int i = 1; i < 3; i++) {
+      for (int j = 1; j < 3; j++) {
+        if (grid[i][j] == 'W') {
+          cnt_w ++;
+        }
+      }
+    }
+    if (cnt_w != 2) return true;
+
+    return false;
+  }
+
+  /**
+   * @brief 138th weekly Q1: key of numbers [E]
+   * basic number ops, very easy
+   *
+   * @param num1 num2 num3
+   * @return int
+   */
+  int generateKey(int num1, int num2, int num3) {
+    int ans = 0;
+    int flag = 1;
+    while (num1 >= 10 || num2 >= 10 || num3 >= 10) {
+      int n1 = num1 % 10;
+      int n2 = num2 % 10;
+      int n3 = num3 % 10;
+      num1 /= 10;
+      num2 /= 10;
+      num3 /= 10;
+      ans = ans + flag * min(min(n1, n2), n3);
+      flag *= 10;
+    }
+    ans = ans + flag * min(min(num1, num2), num3);
+    return ans;
+  }
+
+};

daily/Sep2.cc

@@ -0,0 +1,25 @@
+#include <iostream>
+using namespace std;
+
+class Solution {
+ public:
+  /**
+   * @brief LC2024: maximize the confusion of exam [M]
+   * Sliding window: Time: O(N), Space: O(1)
+   *
+   * @param answerKey
+   * @param k
+   * @return int
+   */
+  int maxConsecutiveAnswers(string answerKey, int k) {
+    int ans = 0, le = 0, cnt[2]{};
+    for (int ri = 0; ri < answerKey.length(); ri++) {
+      cnt[answerKey[ri] >> 1 & 1]++;
+      while (cnt[0] > k & cnt[1] > k) {
+        cnt[answerKey[le++] >> 1 & 1]--;
+      }
+      ans = max(ans, ri - le + 1);
+    }
+    return ans;
+  }
+};