From f8d4dd6131c30de4e8843e77baed8d07378e436c Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Tue, 2 Mar 2021 20:18:28 +0800
Subject: import(solutions): Add leetcode 304.

---
 works/solutions/leetcode/cpp/304.cpp | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 works/solutions/leetcode/cpp/304.cpp

(limited to 'works')

diff --git a/works/solutions/leetcode/cpp/304.cpp b/works/solutions/leetcode/cpp/304.cpp
new file mode 100644
index 0000000..ab22281
--- /dev/null
+++ b/works/solutions/leetcode/cpp/304.cpp
@@ -0,0 +1,35 @@
+#include <vector>
+
+using std::vector;
+
+class NumMatrix {
+private:
+  std::vector<std::vector<int>> prefix_sum_;
+
+public:
+  NumMatrix(vector<vector<int>> &matrix)
+      : prefix_sum_(
+            matrix.size() + 1,
+            std::vector<int>(matrix.empty() ? 1 : matrix.front().size() + 1)) {
+    const int row_count = matrix.size();
+    const int col_count = matrix.empty() ? 0 : matrix.front().size();
+
+    for (int i = 0; i < row_count; i++)
+      for (int j = 0; j < col_count; j++) {
+        prefix_sum_[i + 1][j + 1] = prefix_sum_[i][j + 1] +
+                                    prefix_sum_[i + 1][j] - prefix_sum_[i][j] +
+                                    matrix[i][j];
+      }
+  }
+
+  int sumRegion(int row1, int col1, int row2, int col2) {
+    return prefix_sum_[row1][col1] - prefix_sum_[row2 + 1][col1] -
+           prefix_sum_[row1][col2 + 1] + prefix_sum_[row2 + 1][col2 + 1];
+  }
+};
+
+/**
+ * Your NumMatrix object will be instantiated and called as such:
+ * NumMatrix* obj = new NumMatrix(matrix);
+ * int param_1 = obj->sumRegion(row1,col1,row2,col2);
+ */
\ No newline at end of file
-- 
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