From 8f3ebbdd3d5d301602bdc55890b6d693245e2cea Mon Sep 17 00:00:00 2001
From: Sainnhe Park <i@sainnhe.dev>
Date: Tue, 22 Nov 2022 21:31:25 +0800
Subject: [PATCH] s0039

---
 include/s0039_combination_sum.hpp | 15 +++++++++++++++
 src/s0039_combination_sum.cpp     | 30 ++++++++++++++++++++++++++++++
 tests/s0039_combination_sum.cpp   | 27 +++++++++++++++++++++++++++
 3 files changed, 72 insertions(+)
 create mode 100644 include/s0039_combination_sum.hpp
 create mode 100644 src/s0039_combination_sum.cpp
 create mode 100644 tests/s0039_combination_sum.cpp

diff --git a/include/s0039_combination_sum.hpp b/include/s0039_combination_sum.hpp
new file mode 100644
index 0000000..66dc6e2
--- /dev/null
+++ b/include/s0039_combination_sum.hpp
@@ -0,0 +1,15 @@
+#ifndef S0039_COMBINATION_SUM_HPP
+#define S0039_COMBINATION_SUM_HPP
+
+#include <vector>
+#include <algorithm>
+#include <iterator>
+
+using namespace std;
+
+class Solution {
+ public:
+  vector<vector<int>> combinationSum(vector<int>& candidates, int target);
+};
+
+#endif
diff --git a/src/s0039_combination_sum.cpp b/src/s0039_combination_sum.cpp
new file mode 100644
index 0000000..52907b5
--- /dev/null
+++ b/src/s0039_combination_sum.cpp
@@ -0,0 +1,30 @@
+#include "s0039_combination_sum.hpp"
+
+#include <vector>
+
+void dfs(vector<int>& candidates, int target, vector<vector<int>>& ans,
+         vector<int>& combine, int idx) {
+  if (idx == candidates.size()) {
+    return;
+  }
+  if (target == 0) {
+    ans.emplace_back(combine);
+    return;
+  }
+  // 直接跳过
+  dfs(candidates, target, ans, combine, idx + 1);
+  // 选择当前数
+  if (target - candidates[idx] >= 0) {
+    combine.emplace_back(candidates[idx]);
+    dfs(candidates, target - candidates[idx], ans, combine, idx);
+    combine.pop_back();
+  }
+}
+
+vector<vector<int>> Solution::combinationSum(vector<int>& candidates,
+                                             int target) {
+  vector<vector<int>> ans;
+  vector<int> combine;
+  dfs(candidates, target, ans, combine, 0);
+  return ans;
+}
diff --git a/tests/s0039_combination_sum.cpp b/tests/s0039_combination_sum.cpp
new file mode 100644
index 0000000..082519b
--- /dev/null
+++ b/tests/s0039_combination_sum.cpp
@@ -0,0 +1,27 @@
+#include "s0039_combination_sum.hpp"
+
+#include <gtest/gtest.h>
+
+TEST(Problem39, Case1) {
+  vector<int> candidates{2, 3, 6, 7};
+  int target{7};
+  vector<vector<int>> o{{7}, {2, 2, 3}};
+  Solution solution;
+  EXPECT_EQ(solution.combinationSum(candidates, target), o);
+}
+
+TEST(Problem39, Case2) {
+  vector<int> candidates{2, 3, 5};
+  int target{8};
+  vector<vector<int>> o{{3, 5}, {2, 3, 3}, {2, 2, 2, 2}};
+  Solution solution;
+  EXPECT_EQ(solution.combinationSum(candidates, target), o);
+}
+
+TEST(Problem39, Case3) {
+  vector<int> candidates{2};
+  int target{1};
+  vector<vector<int>> o{};
+  Solution solution;
+  EXPECT_EQ(solution.combinationSum(candidates, target), o);
+}