diff --git a/src/main/java/com/cool/hot100/dp/Num279.java b/src/main/java/com/cool/hot100/dp/Num279.java
index 6d0a90c..b069583 100644
--- a/src/main/java/com/cool/hot100/dp/Num279.java
+++ b/src/main/java/com/cool/hot100/dp/Num279.java
@@ -2,6 +2,8 @@ package com.cool.hot100.dp;
 
 import org.junit.Test;
 
+import java.util.Arrays;
+
 /**
  * Created with IntelliJ IDEA.
  *
@@ -13,8 +15,52 @@ import org.junit.Test;
  */
 public class Num279 {
 
+    private static final int[][] memory = new int[101][10001];
+//
+//    static {
+//        for (int[] row : memory) {
+//            Arrays.fill(row, -1); // -1 表示没有计算过
+//        }
+//    }
+
+    static {
+        for (int[] row : memory) {
+            Arrays.fill(row, Integer.MAX_VALUE); // -1 表示没有计算过
+        }
+        memory[0][0] = 0;
+    }
 
     public int numSquares(int n) {
+        for (int i = 1; i * i <= n; i++) {
+            for (int j = 0; j <= n; j++) {
+                if (j < i * i) {
+                    memory[i][j] = memory[i - 1][j];
+                } else {
+                    memory[i][j] = Math.min(memory[i - 1][j], memory[i][j - i * i] + 1);
+                }
 
+            }
+        }
+        return memory[(int) Math.sqrt(n)][n];
     }
+
+
+    public int numSquares1(int n) {
+        return dfs((int) Math.sqrt(n), n);
+    }
+
+    // i是指j比哪些i的平方大，j为当前数字
+    private int dfs(int i, int j) {
+        if (i == 0) {
+            return j == 0 ? 0 : Integer.MAX_VALUE;
+        }
+        if (memory[i][j] != -1) {
+            return memory[i][j];
+        }
+        if (i * i > j) {
+            return memory[i][j] = dfs(i - 1, j);
+        }
+        return memory[i][j] = Math.min(dfs(i - 1, j), dfs(i, j - i * i) + 1);
+    }
+
 }