solve #118

Author: aylei

src/lib.rs

@@ -116,3 +116,4 @@ mod n0112_path_sum;
 mod n0113_path_sum_ii;
 mod n0114_flatten_binary_tree_to_linked_list;
 mod n0115_distinct_subsequences;
+mod n0118_pascals_triangle;

src/n0118_pascals_triangle.rs

@@ -0,0 +1,64 @@
+/**
+ * [118] Pascal's Triangle
+ *
+ * Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.
+ * 
+ * <img alt="" src="https://upload.wikimedia.org/wikipedia/commons/0/0d/PascalTriangleAnimated2.gif" style="height:240px; width:260px" /><br />
+ * <small>In Pascal's triangle, each number is the sum of the two numbers directly above it.</small>
+ * 
+ * Example:
+ * 
+ * 
+ * Input: 5
+ * Output:
+ * [
+ *      [1],
+ *     [1,1],
+ *    [1,2,1],
+ *   [1,3,3,1],
+ *  [1,4,6,4,1]
+ * ]
+ * 
+ * 
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn generate(num_rows: i32) -> Vec<Vec<i32>> {
+        let mut res = Vec::new();
+        if num_rows < 1 { return res }
+        let mut curr = vec![1];
+        for _ in 0..num_rows {
+            let mut next = vec![1; curr.len()+1];
+            for i in 1..curr.len() {
+                next[i] = curr[i-1] + curr[i];
+            }
+            res.push(curr);
+            curr = next;
+        }
+        res
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_118() {
+        assert_eq!(Solution::generate(1), vec![vec![1]]);
+        assert_eq!(
+            Solution::generate(5),
+            vec![
+                vec![1],
+                vec![1,1],
+                vec![1,2,1],
+                vec![1,3,3,1],
+                vec![1,4,6,4,1]
+            ]);
+    }
+}