Add solution

dynamic-programming/book-shop/README.md

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+# Book Shop
+
+Problem page: <https://cses.fi/problemset/task/1158/>

dynamic-programming/book-shop/main.cpp

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+#include <iostream>
+#include <algorithm>
+#include <vector>
+
+using namespace std;
+
+int main(){
+    int n{}, x{};
+    cin >> n >> x;
+    int h[n], s[n];
+
+    for (auto &x : h) cin >> x;
+    for (auto &x : s) cin >> x;
+
+    vector<vector<int>> memo(n+1, vector<int>(x+1, 0));
+
+    for (int i = 1; i <= n; i++){
+        for (int j = 1; j <= x; j++){
+            memo[i][j] = memo[i-1][j];
+            if(j - h[i-1] >= 0){
+                memo[i][j] = max(memo[i][j], memo[i-1][j-h[i-1]] + s[i-1]);
+            }
+        }
+    }
+    cout << memo[n][x] << "\n";
+
+    return 0;
+}