leetcode

LeetCode 75 II: Day 11

2 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/ Problems/0815.cpp b/ Problems/0815.cpp

@@ -0,0 +1,32 @@

class Solution {

public:

int numBusesToDestination(vector<vector<int>> &routes, int source,

int target) {

if (source == target) return 0;

unordered_map<int, vector<int>> adj;

queue<int> q;

for (int i = 0; i < routes.size(); i++)

for (auto s : routes[i]) adj[s].push_back(i);

if (!adj.count(target)) return -1;

q.push(source);

for (int lvl = 1; !q.empty(); lvl++) {

for (int k = q.size(); k > 0; k--) {

int crnt = q.front();

q.pop();

for (int r : adj[crnt]) {

for (int v : routes[r]) {

if (v == target) return lvl;

q.push(v);

}

routes[r].clear();

}

adj[crnt].clear();

}

}

return -1;

}

};

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

@@ -288,6 +288,7 @@ for solving problems. | 0787 | Medium | [Cheapest Flights Within K Stops](Problems/0787.cpp) | | 0797 | Medium | [All Paths From Source to Target](Problems/0797.cpp) | | 0802 | Medium | [Find Eventual Safe States](Problems/0802.cpp) |

| 0815 | Hard | [Bus Routes](Problems/0815.cpp) |

| 0830 | Medium | [Kth Smallest Element in a BST](Problems/0230.cpp) | | 0841 | Medium | [Keys and Rooms](Problems/0841.cpp) | | 0844 | Easy | [Backspace String Compare](Problems/0844.cpp) |