Ways of Coin Change | Bottom-up | O(N*M) time with O(N) extra space

Author: SteffiKeranJ

Dynamic-Programming/change.cpp

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+class Solution {
+public:
+    int change(int amount, vector<int>& coins) {
+        int n = coins.size();
+        vector<int> dp(amount+1);        // bottom-up approach
+        dp[0] = 1;  // because only way if no change
+        for(int i = 0; i < n; ++i) {
+            for(int j = 1; j <amount+1; ++j) {
+                if (coins[i] <= j) {
+                    dp[j] += dp[j - coins[i]];
+                }
+            }
+        }
+        return dp[amount];
+    }
+};