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source/DP/SoS.cpp

@@ -0,0 +1,22 @@
+int n = 20;
+vector<int> a(1 << n);
+
+// keeps track of the sum over subsets
+// with a certain amount of matching bits in the prefix
+vector<vector<int>> dp(1 << n, vector<int>(n));
+
+vector<int> sos(1 << n);
+for (int mask = 0; mask < (1 << n); mask++) {
+	dp[mask][-1] = a[mask];
+	for (int x = 0; x < n; x++) {
+		dp[mask][x] = dp[mask][x - 1];
+		if (mask & (1 << x)) { dp[mask][x] += dp[mask - (1 << x)][x - 1]; }
+	}
+	sos[mask] = dp[mask][n - 1];
+}
+
+////////////////////////////////////////////
+D[i]에 미리 i에 해당하는 값을 넣어둔다
+fors(d, 0, 19) fors(i,0,(1<<20)-1)
+    if(i & (1<<d)) D[i] += D[i^(1<<d)];
+-> D[i] : sum of subset of mask i