Cheapest Flights Within K Stops
so ive seen many solutions for the problem. here is a link to the full problem https://leetcode.com/problems/cheapest-flights-within-k-stops/description/.
It asks for the cheapest path from src to dest with upto K stops. most solutions use bellman ford (slightly modified with k+1 itterations) to solve it. The only way i could get BF to work, is by modifying it like i found in many online solutions by using a TEMP storage vector (see below) . the vector temp_dp(dp) confuses me.. what ive seen from BFs algorithm is that you relax an edge U->V and change V in the distance vector. here theyre changing it in a temp vector and reassigning it (which makes it work) can anyone explain how this works.
int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int K) {
vector<int> dp(n, INT_MAX);
dp[src] = 0;
for(int z = 0; z <= K; z++){
vector<int> temp_dp(dp);
for(auto e: flights) {
if (dp[e[0]] < INT_MAX) {
temp_dp[e[1]] = min(temp_dp[e[1]], dp[e[0]] + e[2]);
}
}
dp = temp_dp;
}
return dp[dst] == INT_MAX ? -1 : dp[dst];
}
graph shortest-path bellman-ford
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
add a comment |
so ive seen many solutions for the problem. here is a link to the full problem https://leetcode.com/problems/cheapest-flights-within-k-stops/description/.
It asks for the cheapest path from src to dest with upto K stops. most solutions use bellman ford (slightly modified with k+1 itterations) to solve it. The only way i could get BF to work, is by modifying it like i found in many online solutions by using a TEMP storage vector (see below) . the vector temp_dp(dp) confuses me.. what ive seen from BFs algorithm is that you relax an edge U->V and change V in the distance vector. here theyre changing it in a temp vector and reassigning it (which makes it work) can anyone explain how this works.
int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int K) {
vector<int> dp(n, INT_MAX);
dp[src] = 0;
for(int z = 0; z <= K; z++){
vector<int> temp_dp(dp);
for(auto e: flights) {
if (dp[e[0]] < INT_MAX) {
temp_dp[e[1]] = min(temp_dp[e[1]], dp[e[0]] + e[2]);
}
}
dp = temp_dp;
}
return dp[dst] == INT_MAX ? -1 : dp[dst];
}
graph shortest-path bellman-ford
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
add a comment |
so ive seen many solutions for the problem. here is a link to the full problem https://leetcode.com/problems/cheapest-flights-within-k-stops/description/.
It asks for the cheapest path from src to dest with upto K stops. most solutions use bellman ford (slightly modified with k+1 itterations) to solve it. The only way i could get BF to work, is by modifying it like i found in many online solutions by using a TEMP storage vector (see below) . the vector temp_dp(dp) confuses me.. what ive seen from BFs algorithm is that you relax an edge U->V and change V in the distance vector. here theyre changing it in a temp vector and reassigning it (which makes it work) can anyone explain how this works.
int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int K) {
vector<int> dp(n, INT_MAX);
dp[src] = 0;
for(int z = 0; z <= K; z++){
vector<int> temp_dp(dp);
for(auto e: flights) {
if (dp[e[0]] < INT_MAX) {
temp_dp[e[1]] = min(temp_dp[e[1]], dp[e[0]] + e[2]);
}
}
dp = temp_dp;
}
return dp[dst] == INT_MAX ? -1 : dp[dst];
}
graph shortest-path bellman-ford
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
so ive seen many solutions for the problem. here is a link to the full problem https://leetcode.com/problems/cheapest-flights-within-k-stops/description/.
It asks for the cheapest path from src to dest with upto K stops. most solutions use bellman ford (slightly modified with k+1 itterations) to solve it. The only way i could get BF to work, is by modifying it like i found in many online solutions by using a TEMP storage vector (see below) . the vector temp_dp(dp) confuses me.. what ive seen from BFs algorithm is that you relax an edge U->V and change V in the distance vector. here theyre changing it in a temp vector and reassigning it (which makes it work) can anyone explain how this works.
int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int K) {
vector<int> dp(n, INT_MAX);
dp[src] = 0;
for(int z = 0; z <= K; z++){
vector<int> temp_dp(dp);
for(auto e: flights) {
if (dp[e[0]] < INT_MAX) {
temp_dp[e[1]] = min(temp_dp[e[1]], dp[e[0]] + e[2]);
}
}
dp = temp_dp;
}
return dp[dst] == INT_MAX ? -1 : dp[dst];
}
graph shortest-path bellman-ford
graph shortest-path bellman-ford
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
asked Nov 21 '18 at 2:43
Omar HamdanOmar Hamdan
12
12
add a comment |
add a comment |
0
active
oldest
votes
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53404584%2fcheapest-flights-within-k-stops%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
0
active
oldest
votes
0
active
oldest
votes
active
oldest
votes
active
oldest
votes
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53404584%2fcheapest-flights-within-k-stops%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
