dijkstra

• 已經確定最短的頂點數組【U】 【U】+【u】【v】 < 【v】，那么就更新
• 每次找到還沒有確定的最小數值
• 先確認一個最小值
  • 之后再從這個數值出來，到V距離之和與V進行比較

//Given a signed 32-bit integer x, return x with its digits reversed. If reversi //ng x causes the value to go outside the signed 32-bit integer range [-231, 231 - // 1], then return 0. // // Assume the environment does not allow you to store 64-bit integers (signed or // unsigned). // // // Example 1: // Input: x = 123 //Output: 321 // Example 2: // Input: x = -123 //Output: -321 // Example 3: // Input: x = 120 //Output: 21 // Example 4: // Input: x = 0 //Output: 0 // // // Constraints: // // // -231 <= x <= 231 - 1 // // Related Topics 數學 // 👍 2958 👎 0// A C++ program for Dijkstra's single source shortest path algorithm. // The program is for adjacency matrix representation of the graph #include <iostream> using namespace std; #include <limits.h>// Number of vertices in the graph #define V 9// A utility function to find the vertex with minimum distance value, from // the set of vertices not yet included in shortest path tree int minDistance(int dist[], bool sptSet[]) {// Initialize min valueint min = INT_MAX, min_index;for (int v = 0; v < V; v++)if (sptSet[v] == false && dist[v] <= min)min = dist[v], min_index = v;return min_index; }// A utility function to print the constructed distance array void printSolution(int dist[]) {cout <<"Vertex \t Distance from Source" << endl;for (int i = 0; i < V; i++)cout << i << " \t\t"<<dist[i]<< endl; }// Function that implements Dijkstra's single source shortest path algorithm // for a graph represented using adjacency matrix representation void dijkstra(int graph[V][V], int src) {int dist[V]; // The output array. dist[i] will hold the shortest// distance from src to ibool sptSet[V]; // sptSet[i] will be true if vertex i is included in shortest// path tree or shortest distance from src to i is finalized// Initialize all distances as INFINITE and stpSet[] as falsefor (int i = 0; i < V; i++)dist[i] = INT_MAX, sptSet[i] = false;// Distance of source vertex from itself is always 0dist[src] = 0;// Find shortest path for all verticesfor (int count = 0; count < V - 1; count++) {// Pick the minimum distance vertex from the set of vertices not// yet processed. u is always equal to src in the first iteration.int u = minDistance(dist, sptSet);// Mark the picked vertex as processedsptSet[u] = true;// Update dist value of the adjacent vertices of the picked vertex.for (int v = 0; v < V; v++)// Update dist[v] only if is not in sptSet, there is an edge from// u to v, and total weight of path from src to v through u is// smaller than current value of dist[v]if (!sptSet[v] && graph[u][v] && dist[u] != INT_MAX&& dist[u] + graph[u][v] < dist[v])dist[v] = dist[u] + graph[u][v];}// print the constructed distance arrayprintSolution(dist); }// driver program to test above function int main() {/* Let us create the example graph discussed above */int graph[V][V] = { { 0, 4, 0, 0, 0, 0, 0, 8, 0 },{ 4, 0, 8, 0, 0, 0, 0, 11, 0 },{ 0, 8, 0, 7, 0, 4, 0, 0, 2 },{ 0, 0, 7, 0, 9, 14, 0, 0, 0 },{ 0, 0, 0, 9, 0, 10, 0, 0, 0 },{ 0, 0, 4, 14, 10, 0, 2, 0, 0 },{ 0, 0, 0, 0, 0, 2, 0, 1, 6 },{ 8, 11, 0, 0, 0, 0, 1, 0, 7 },{ 0, 0, 2, 0, 0, 0, 6, 7, 0 } };dijkstra(graph, 0);return 0; }// This code is contributed by shivanisinghss2110//leetcode submit region end(Prohibit modification and deletion)

2:leetcode 754 題目

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