Solve #279

Author: aylei

src/lib.rs

@@ -214,3 +214,4 @@ mod n0268_missing_number;
 mod n0273_integer_to_english_words;
 mod n0274_h_index;
 mod n0275_h_index_ii;
+mod n0279_perfect_squares;

src/n0279_perfect_squares.rs

@@ -0,0 +1,56 @@
+/**
+ * [279] Perfect Squares
+ *
+ * Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...) which sum to n.
+ *
+ * Example 1:
+ *
+ *
+ * Input: n = 12
+ * Output: 3
+ * Explanation: 12 = 4 + 4 + 4.
+ *
+ * Example 2:
+ *
+ *
+ * Input: n = 13
+ * Output: 2
+ * Explanation: 13 = 4 + 9.
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+// BFS
+use std::collections::VecDeque;
+impl Solution {
+    pub fn num_squares(n: i32) -> i32 {
+        if n < 1 { return 0 }
+        let mut deq = VecDeque::new();
+        deq.push_back((1,n));
+        while let Some((level, num)) = deq.pop_front() {
+            let mut base = 1;
+            while base * base <= num {
+                if base * base == num {
+                    return level
+                }
+                deq.push_back((level + 1, num - base * base));
+                base += 1;
+            }
+        }
+        0
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_279() {
+        assert_eq!(Solution::num_squares(13), 2);
+        assert_eq!(Solution::num_squares(12), 3);
+    }
+}