solve #64

Author: aylei

src/lib.rs

@@ -64,3 +64,4 @@ mod n0060_permutation_sequence;
 mod n0061_rotate_list;
 mod n0062_unique_paths;
 mod n0063_unique_paths_ii;
+mod n0064_minimum_path_sum;

src/n0064_minimum_path_sum.rs

@@ -0,0 +1,78 @@
+/**
+ * [64] Minimum Path Sum
+ *
+ * Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.
+ * 
+ * Note: You can only move either down or right at any point in time.
+ * 
+ * Example:
+ * 
+ * 
+ * Input:
+ * [
+ *   [1,3,1],
+ *   [1,5,1],
+ *   [4,2,1]
+ * ]
+ * Output: 7
+ * Explanation: Because the path 1→3→1→1→1 minimizes the sum.
+ * 
+ * 
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn min_path_sum(grid: Vec<Vec<i32>>) -> i32 {
+        let (height, width) = (grid.len(), grid[0].len());
+        let mut grid = grid;
+        let mut step = 1;
+        while step <= height + width - 2 {
+            for x in 0..(step+1) {
+                let y = step - x;
+                if x >= height || y >= width { continue }
+                if x < 1 {
+                    grid[x][y] += grid[x][y-1];
+                } else if y < 1 {
+                    grid[x][y] += grid[x-1][y];
+                } else {
+                    grid[x][y] += i32::min(grid[x][y-1], grid[x-1][y]);
+                }
+            }
+            step += 1;
+        }
+        grid[height-1][width-1]
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_64() {
+        assert_eq!(
+            Solution::min_path_sum(vec![vec![2]]),
+            2
+        );
+        assert_eq!(
+            Solution::min_path_sum(
+                vec![
+                    vec![1,3,1],
+                    vec![1,5,1],
+                    vec![4,2,1],
+                ]),
+            7
+        );
+        assert_eq!(
+            Solution::min_path_sum(
+                vec![
+                    vec![1,3,1],
+                ]),
+            5
+        );
+    }
+}