Solve #304

Author: aylei

src/lib.rs

@@ -226,3 +226,4 @@ mod n0299_bulls_and_cows;
 mod n0300_longest_increasing_subsequence;
 mod n0301_remove_invalid_parentheses;
 mod n0303_range_sum_query_immutable;
+mod n0304_range_sum_query_2d_immutable;

src/n0304_range_sum_query_2d_immutable.rs

@@ -0,0 +1,105 @@
+/**
+ * [304] Range Sum Query 2D - Immutable
+ *
+ * Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2).
+ *
+ *
+ * <img src="/static/images/courses/range_sum_query_2d.png" border="0" alt="Range Sum Query 2D" /><br />
+ * <small>The above rectangle (with the red border) is defined by (row1, col1) = (2, 1) and (row2, col2) = (4, 3), which contains sum = 8.</small>
+ *
+ *
+ * Example:<br>
+ *
+ * Given matrix = [
+ *   [3, 0, 1, 4, 2],
+ *   [5, 6, 3, 2, 1],
+ *   [1, 2, 0, 1, 5],
+ *   [4, 1, 0, 1, 7],
+ *   [1, 0, 3, 0, 5]
+ * ]
+ *
+ * sumRegion(2, 1, 4, 3) -> 8
+ * sumRegion(1, 1, 2, 2) -> 11
+ * sumRegion(1, 2, 2, 4) -> 12
+ *
+ *
+ *
+ * Note:<br>
+ * <ol>
+ * You may assume that the matrix does not change.
+ * There are many calls to sumRegion function.
+ * You may assume that row1 &le; row2 and col1 &le; col2.
+ * </ol>
+ *
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+struct NumMatrix {
+    cache: Vec<Vec<i32>>
+}
+
+/**               region[2, 2, 3, 4] =
+ *  x x \ \ \ .     square[3,4] - square[1,4] - square[3,1] + square[1,1]
+ *  x x \ \ \ .
+ *  / / o o o .
+ *  / / o o o .
+ *  . . . . . .
+ *  . . . . . .
+ */
+impl NumMatrix {
+    fn new(matrix: Vec<Vec<i32>>) -> Self {
+        if matrix.is_empty() || matrix[0].is_empty() {
+            return NumMatrix{cache: vec![vec![]]}
+        }
+        let (x_max, y_max) = (matrix.len(), matrix[0].len());
+        let mut cache = vec![vec![0; y_max]; x_max];
+        for x in 0..x_max {
+            for y in 0..y_max {
+                cache[x][y] =  matrix[x][y] +
+                    if y > 0 { cache[x][y-1] } else { 0 } +
+                    if x > 0 { cache[x-1][y] } else { 0 } -
+                    if x > 0 && y > 0 { cache[x-1][y-1] } else { 0 }
+            }
+        }
+        NumMatrix{cache: cache}
+    }
+
+    fn sum_region(&self, row1: i32, col1: i32, row2: i32, col2: i32) -> i32 {
+        let (row1,col1,row2,col2) = (row1 as usize, col1 as usize, row2 as usize, col2 as usize);
+        self.cache[row2][col2] -
+            if row1 > 0 { self.cache[row1-1][col2] } else { 0 } -
+            if col1 > 0 { self.cache[row2][col1-1] } else { 0 } +
+            if row1 > 0 && col1 > 0 { self.cache[row1-1][col1-1]} else { 0 }
+    }
+}
+
+/**
+ * Your NumMatrix object will be instantiated and called as such:
+ * let obj = NumMatrix::new(matrix);
+ * let ret_1: i32 = obj.sum_region(row1, col1, row2, col2);
+ */
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_304() {
+        let matrix = NumMatrix::new(
+            vec![
+                vec![3, 0, 1, 4, 2],
+                vec![5, 6, 3, 2, 1],
+                vec![1, 2, 0, 1, 5],
+                vec![4, 1, 0, 1, 7],
+                vec![1, 0, 3, 0, 5]
+            ]
+        );
+        assert_eq!(matrix.sum_region(1, 1, 2, 2), 11);
+        assert_eq!(matrix.sum_region(2, 1, 4, 3), 8);
+        assert_eq!(matrix.sum_region(1, 2, 2, 4), 12);
+    }
+}