fd

Author: dingjikerbo

README.md

@@ -288,6 +288,7 @@
 |317|[Shortest Distance from All Buildings](https://leetcode.com/problems/shortest-distance-from-all-buildings/)| [Java](leetcode/solution/src/ShortestDistanceFromAllBuildings.java)|75|典型的bfs，多做两遍|
 |319|[Bulb Switcher](https://leetcode.com/problems/bulb-switcher/)| [Java](leetcode/solution/src/BulbSwitcher.java)|90|
 |320|[Generalized Abbreviation](https://leetcode.com/problems/generalized-abbreviation/)| [Java](leetcode/solution/src/GeneralizedAbbreviation.java)|70|这题是典型的back tracking，多做几遍|
+|322|[Coin Change](https://leetcode.com/problems/coin-change/)|[Java](leetcode/solution/src/CoinChange.java)|80||
 |323|[Number of Connected Components in an Undirected Graph](https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/)| [Java](leetcode/solution/src/NumberOfConnectedComponents.java)|90|典型的图，多看两遍|
 |324|[Wiggle Sort II](https://leetcode.com/problems/wiggle-sort-ii/)| [Java](leetcode/solution/src/WiggleSortII.java)|60|
 |325|[Maximum Size Subarray Sum Equals k](https://leetcode.com/problems/maximum-size-subarray-sum-equals-k/)| [Java](leetcode/solution/src/MaximumSizeSubarraySumEqualsK.java)|75|这题思路有意思，多做几遍|

leetcode/solution/src/CoinChange.java

@@ -0,0 +1,20 @@
+import java.util.Arrays;
+
+public class CoinChange {
+
+    public int coinChange(int[] coins, int amount) {
+        Arrays.sort(coins);
+        int[] dp = new int[amount + 1];
+        Arrays.fill(dp, -1);
+        dp[0] = 0;
+        for (int i = 1; i <= amount; i++) {
+            for (int coin: coins) {
+                if (i - coin >= 0 && dp[i - coin] >= 0) {
+                    int k = dp[i - coin] + 1;
+                    dp[i] = dp[i] > 0 ? Math.min(dp[i], k) : k;
+                }
+            }
+        }
+        return dp[amount];
+    }
+}

leetcode/src/Main.java

@@ -2,33 +2,25 @@
 
 public class Main {
 
-    public int maxAreaOfIsland(int[][] grid) {
-        int[] area = new int[1];
-        int max = 0;
-
-        for (int i = 0; i < grid.length; i++) {
-            for (int j = 0; j < grid[0].length; j++) {
-                area[0] = 0;
-                dfs(grid, i, j, area);
-                max = Math.max(max, area[0]);
+    public static int coinChange(int[] coins, int amount) {
+        Arrays.sort(coins);
+        int[] dp = new int[amount + 1];
+        Arrays.fill(dp, -1);
+        dp[0] = 0;
+        for (int i = 1; i <= amount; i++) {
+            for (int coin: coins) {
+                if (i - coin >= 0 && dp[i - coin] >= 0) {
+                    int k = dp[i - coin] + 1;
+                    dp[i] = dp[i] > 0 ? Math.min(dp[i], k) : k;
+                }
             }
         }
-        return max;
-    }
-
-    private void dfs(int[][] grid, int i, int j, int[] count) {
-        if (i < 0 || i >= grid.length || j < 0 || j >= grid[0].length || grid[i][j] != 1) {
-            return;
-        }
-        grid[i][j] = 0;
-        count[0]++;
-        dfs(grid, i + 1, j, count);
-        dfs(grid, i - 1, j, count);
-        dfs(grid, i, j + 1, count);
-        dfs(grid, i, j - 1, count);
+        return dp[amount];
     }
 
     public static void main(String[] args) {
-
+        System.out.println(coinChange(new int[] {
+                1, 2, 5
+        }, 11));
     }
 }