solved 4 problems.

Author: coderfive

112.Path Sum/coderfive/112.cc

@@ -0,0 +1,11 @@
+class Solution {
+public:
+    bool hasPathSum(TreeNode* root, int sum) {
+	if (!root) return false;
+	sum -= root->val;
+	if (root->left && hasPathSum(root->left, sum)) return true;
+	if (root->right && hasPathSum(root->right, sum)) return true;
+	if (!root->left && !root->right && sum == 0) return true;
+	return false;
+    }
+};

113.Path Sum II/coderfive/113.cc

@@ -0,0 +1,20 @@
+class Solution {
+public:
+    vector<vector<int>> pathSum(TreeNode* root, int sum) {
+	vector<vector<int>> res;
+	vector<int> v;
+	helper(root, res, v, sum);
+	return res;
+    }
+    void helper (TreeNode* root, vector<vector<int>>& res, vector<int>& path, int sum) {
+	if (!root) return;
+	path.push_back(root->val);
+	sum -= root->val;
+	if (!root->left && !root->right && sum == 0)
+	    res.push_back(path);
+	helper(root->left, res, path, sum);
+	helper(root->right, res, path, sum);
+
+	path.pop_back();
+    }
+};

114.Flatten Binary Tree to Linked List/coderfive/114.cc

@@ -0,0 +1,20 @@
+class Solution {
+public:
+    void flatten(TreeNode* root) {
+	if (!root) return;
+	helper(root);
+    }
+    TreeNode* helper (TreeNode* root) {
+	TreeNode* cur = root, *right = root->right;
+	if (root->left) {
+	    root->right = root->left;
+	    cur = helper(root->left);
+	    root->left = NULL;
+	}
+	if (right) {
+	    cur->right = right;
+	    cur = helper(right);
+	}
+	return cur;
+    }
+};

115.Distinct Subsequences/coderfive/115.cc

@@ -0,0 +1,32 @@
+#include <map>
+#include <vector>
+#include <string>
+#include <iostream>
+using namespace std;
+
+class Solution {
+public:
+    int numDistinct(string s, string t) {
+	if (s.size() == 0 || t.size() == 0) return 0;
+	if (t.size() > s.size()) return 0;
+	vector<int> v (t.size(), 0);
+	map<char, vector<int>> mp;
+	for (int i = 0; i < t.size(); i++)
+	    mp[t[i]].push_back(i);
+	for (auto a : s) {
+	    vector<int>& idx = mp[a];
+	    for (auto it = idx.rbegin(); it != idx.rend(); it++)
+		if (*it == 0) v[*it]++;
+		else v[*it] += v[*it-1];
+	}
+
+	return v.back();
+    }
+};
+
+int main() {
+    std::cout << Solution().numDistinct("ccc", "c") << std::endl;
+    std::cout << Solution().numDistinct("ccc", "cc") << std::endl;
+
+    return 0;
+}