add: 220520 [cpp]

cpp/2205/220520.cpp

@@ -0,0 +1,52 @@
+#include <vector>
+#include <cstdio>
+#include <algorithm>
+
+/**
+ * 63. Unique Paths II
+ * You are given an m x n integer array grid. There is a robot initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m-1][n-1]). The robot can only move either down or right at any point in time.
+ * An obstacle and space are marked as 1 or 0 respectively in grid. A path that the robot takes cannot include any square that is an obstacle.
+ * Return the number of possible unique paths that the robot can take to reach the bottom-right corner.
+ * The testcases are generated so that the answer will be less than or equal to 2 * 109.
+ */
+
+class Solution {
+public:
+	static int uniquePathsWithObstacles(const std::vector<std::vector<int>>& obstacleGrid) {
+		const int m = obstacleGrid.size(), n = obstacleGrid.front().size(), k = std::min(m, n);
+		auto* dp = new unsigned[n * m]{static_cast<unsigned int>(obstacleGrid[0][0] ^ 1)};
+
+		for (int i = 1; i < k; ++i) {
+			dp[i * n] = obstacleGrid[i][0] ? 0 : dp[(i - 1) * n]; // X axis
+			dp[i] = obstacleGrid[0][i] ? 0 : dp[i - 1]; // Y axis
+			for (int j = 1; j < i; ++j) {
+				dp[i * n + j] = obstacleGrid[i][j] ? 0 : (dp[i * n + j - 1] + dp[(i - 1) * n + j]);
+				dp[i + n * j] = obstacleGrid[j][i] ? 0 : (dp[i - 1 + n * j] + dp[i + n * (j - 1)]);
+			}
+			dp[i * n + i] = obstacleGrid[i][i] ? 0 : (dp[i - 1 + i * n] + dp[(i - 1) * n + i]);
+		}
+
+		if (m > n) {
+			for (int i = k; i < m; ++i) {
+				dp[i * n] = obstacleGrid[i][0] ? 0 : dp[(i - 1) * n]; // X axis
+				for (int j = 1; j < n; ++j)
+					dp[i * n + j] = obstacleGrid[i][j] ? 0 : (dp[i * n + j - 1] + dp[(i - 1) * n + j]);
+			}
+		} else if (n > m) {
+			for (int i = k; i < n; ++i) {
+				dp[i] = obstacleGrid[0][i] ? 0 : dp[i - 1]; // Y axis
+				for (int j = 1; j < m; ++j)
+					dp[i + n * j] = obstacleGrid[j][i] ? 0 : (dp[i - 1 + n * j] + dp[i + n * (j - 1)]);
+			}
+		}
+
+		auto ret = dp[m * n - 1];
+		delete[] dp;
+		return ret;
+	}
+};
+
+int main() {
+	std::printf("%d\n", Solution::uniquePathsWithObstacles({{0,1,0,0,0},{1,0,0,0,0},{0,0,0,0,0},{0,0,0,0,0}}));
+	return 0;
+}

cpp/2205/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2205)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2205 220520-CN.cpp)
+ADD_EXECUTABLE(2205 220520.cpp)