leetcode

LeetCode 75 II: Day 7

2 files changed, 71 insertions(+), 0 deletions(-)

diff --git a/ Problems/0437.cpp b/ Problems/0437.cpp

@@ -0,0 +1,70 @@

// Brute force

class Solution {

public:

int pathSum(TreeNode *root, int targetSum) {

if (!root) return 0;

stack<TreeNode *> st;

queue<TreeNode *> q;

st.push(root);

while (!st.empty()) {

TreeNode *root = st.top();

st.pop();

q.push(root);

if (root->left) st.push(root->left);

if (root->right) st.push(root->right);

}

int res = 0;

while (!q.empty()) {

stack<pair<TreeNode *, long long>> st;

st.push({q.front(), 0});

q.pop();

while (!st.empty()) {

auto [root, sum] = st.top();

st.pop();

sum += root->val;

if (sum == targetSum) res++;

if (root->left) st.push({root->left, sum});

if (root->right) st.push({root->right, sum});

}

}

return res;

}

};

// Optimized

class Solution {

public:

int pathSum(TreeNode *root, int targetSum) {

if (!root) return 0;

queue<pair<TreeNode *, vector<long long>>> q;

int res = 0;

q.push({root, {}});

while (!q.empty()) {

auto &[root, vec] = q.front();

long long sum = root->val + (vec.size() ? vec.back() : 0);

for (int num : vec)

if (sum - num == targetSum) res++;

if (sum == targetSum) res++;

if (root->left) {

q.push({root->left, vec});

q.back().second.push_back(sum);

}

if (root->right) {

q.push({root->right, vec});

q.back().second.push_back(sum);

}

q.pop();

}

return res;

}

};

diff --git a/ README.md b/ README.md

@@ -209,6 +209,7 @@ for solving problems. | 0430 | Medium | [Flatten a Multilevel Doubly Linked list](Problems/0430.cpp) | | 0433 | Medium | [Minimum Genetic Mutation](Problems/0433.cpp) | | 0435 | Medium | [Non-overlapping Intervals](Problems/0435.cpp) |

| 0437 | Medium | [Path Sum III](Problems/0437.cpp) |

| 0438 | Medium | [Find All Anagrams in a String](Problems/0438.cpp) | | 0445 | Medium | [Add Two Numbers II](Problems/0445.cpp) | | 0448 | Easy | [Find All Numbers Disappeared in an Array](Problems/0448.cpp) |