Coin change

Author: giaunv

datastructure-algorithm-java-examples/src/main/java/com/hellokoding/algorithm/DP_CoinChange.java

@@ -1,5 +1,7 @@
 package com.hellokoding.algorithm;
 
+import java.util.Arrays;
+
 public class DP_CoinChange {
     static int countWays(int[] coins, int targetCoinChange) {
         int[] wayOfCoinChanges = new int[targetCoinChange+1];
@@ -10,12 +12,29 @@ static int countWays(int[] coins, int targetCoinChange) {
             for (int j = coins[i]; j <= targetCoinChange; j++) {
                 wayOfCoinChanges[j] += wayOfCoinChanges[j - coins[i]];
             }
+            System.out.println(Arrays.toString(wayOfCoinChanges));
         }
 
         return wayOfCoinChanges[targetCoinChange];
     }
 
     public static void main(String[] args) {
         System.out.println(countWays(new int[]{2, 3, 1}, 4));
+
+        /*
+        * w[0] = 1
+        * i=0, j=2, w[2] = 0 + w[2-2] = 0 + w[0] = 1
+        * w[3] = w[3] + w[3-2] = w[3] + w[1] = 0 + 0 = 0
+        * w[4] = w[4] + w[4-2] = 0 + w[2] = 1
+        *
+        * i=1, j=3, w[3] = w[3] + w[3-3] = 1
+        * w[4] = w[4] + w[1] = 1
+        *
+        * i=2, j=1, w[1] = w[1] + w[0] = 1
+        * j=2 w[2] = w[2] + w[1] = 2
+        * j=3 w[3] = w[3] + w[2] = 3
+        * j=4 w[4] = w[4] + w[3] = 4
+        *
+        * */
     }
 }

datastructure-algorithm-java-examples/src/main/java/com/hellokoding/algorithm/DP_UniquePaths_Obstacles.java

@@ -2,13 +2,13 @@
 
 public class DP_UniquePaths_Obstacles {
     int countUniquePaths(int[][] A) {
+        if (A[0][0] == 1) return 0;
+
         int rows = A.length;
         int cols = A[0].length;
-
         int[][] cache = new int[rows][cols];
 
-        if (A[0][0] == 0)
-            cache[0][0] = 1;
+        cache[0][0] = 1;
 
         for (int i = 1; i < rows; i++) {
             if (A[i][0] == 0)