diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 30785e6..047020a 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -130,4 +130,5 @@ mod p49_group_anagrams;
 mod p202_happy_number;
 mod p219_contains_duplicate_ii;
 mod p128_longest_consecutive_sequence;
-mod p228_summary_ranges;
\ No newline at end of file
+mod p228_summary_ranges;
+mod p56_merge_intervals;
\ No newline at end of file
diff --git a/src/problem/p56_merge_intervals.rs b/src/problem/p56_merge_intervals.rs
new file mode 100644
index 0000000..026be90
--- /dev/null
+++ b/src/problem/p56_merge_intervals.rs
@@ -0,0 +1,47 @@
+/**
+ * [56] Merge Intervals
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn merge(intervals: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
+        let mut intervals: Vec<(i32, i32)> = intervals.iter().map(|p| (p[0], p[1])).collect();
+
+        intervals.sort_unstable();
+
+        let mut result: Vec<(i32, i32)> = vec![intervals[0]];
+        let mut last = 0;
+
+        for i in 1..intervals.len() {
+            let (begin, end) = intervals[i];
+            let (last_begin, last_end) = result[last];
+
+            if begin <= last_end {
+                result[last].0 = result[last].0.min(begin);
+                result[last].1 = result[last].1.max(end);
+            } else {
+                result.push(intervals[i]);
+                last += 1;
+            }
+        }
+
+        result.iter().map(|p| vec![p.0, p.1]).collect()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_56() {
+        assert_eq!(
+            vec![vec![1, 6], vec![8, 10], vec![15, 18]],
+            Solution::merge(vec![vec![1, 3], vec![2, 6], vec![8, 10], vec![15, 18]])
+        )
+    }
+}