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| author | crupest <crupest@outlook.com> | 2021-03-02 20:18:28 +0800 |
|---|---|---|
| committer | crupest <crupest@outlook.com> | 2021-03-02 20:18:28 +0800 |
| commit | 81617350aae27e287c6d9e044bc3e94ae4f6d048 (patch) | |
| tree | 7582a89e08f3f26fe8126fc88abd278c5f2ca8ba /leetcode | |
| parent | 5c32574dd3b591af160c4de8ba7310aff5152e35 (diff) | |
| download | solutions-81617350aae27e287c6d9e044bc3e94ae4f6d048.tar.gz solutions-81617350aae27e287c6d9e044bc3e94ae4f6d048.tar.bz2 solutions-81617350aae27e287c6d9e044bc3e94ae4f6d048.zip | |
Add leetcode 304.
Diffstat (limited to 'leetcode')
| -rw-r--r-- | leetcode/cpp/304.cpp | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/leetcode/cpp/304.cpp b/leetcode/cpp/304.cpp new file mode 100644 index 0000000..ab22281 --- /dev/null +++ b/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 |