hiho1092_have lunch together

题目

    两个人从同一个点出发，在一个餐厅中寻找两个相邻的座位，需要是的从出发点到达座位的距离总和最短。题目链接: Have Lunch Together
    最短路程，一开始以为要用dijkstra等图算法，发现完全不用，直接用BFS进行搜索，并标记到达每个点的最短距离。一次BFS求出从起始点 到达所有点的最短距离之后，再遍历每个点，判断该点是否是合法的座位（能够从起始点到达，且为座位），然后对每个座位，看它四周的点是否是合法的座位，然 后求出两个合法的座位的最短距离和的最小值。

实现

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#include<stdio.h> #include<cmath> #include<iostream> #include<string.h> #include<algorithm> #include<queue> #include<stack> #include<map> #include<deque> #include<string> #include<unordered_map> #include<unordered_set> using namespace std; #define min(a, b) (a) < (b)? (a) : (b) char gMap[105][105]; int gMinDist[105][105]; int gMoveStep[4][2] = { {-1, 0}, {0, 1}, {1, 0}, {0, -1} }; struct Node {     int row;     int col;     int step;     Node(int r, int c, int s) :         row(r), col(c), step(s) {}; }; //BFS 求出从出发点到达每个能够到达的点的最短距离 void Bfs(int start_row, int start_col) {     queue<Node> Q;     Node node(start_row, start_col, 0);     Q.push(node);     gMinDist[start_row][start_col] = 0;     while (!Q.empty()) {         node = Q.front();         Q.pop();         for (int i = 0; i < 4; i++) {             int next_row = node.row + gMoveStep[i][0];             int next_col = node.col + gMoveStep[i][1];             if ((gMap[next_row][next_col] == 'S' || gMap[next_row][next_col] == '.') && gMinDist[next_row][next_col] == -1) {                 gMinDist[next_row][next_col] = node.step + 1;                 if(gMap[next_row][next_col] == '.')                     Q.push({ next_row, next_col, node.step + 1 });             }         }     } } int MinDist(int n, int m) {     int min_dist = 1 << 29;     for (int i = 1; i <= n; i++) {         for (int j = 1; j <= m; j++) {             if (gMap[i][j] == 'S' && gMinDist[i][j] != -1) { // 为一个座位，且在BFS过程中能够到达                 for (int k = 0; k < 4; k++) {                     int ii = i + gMoveStep[k][0];                     int jj = j + gMoveStep[k][1];                     // 为一个座位，且在BFS过程中能够到达                     if (ii >= 1 && ii <= n && jj >= 1 && jj <= m && gMap[ii][jj] == 'S' && gMinDist[ii][jj] != -1) {                         min_dist = min(min_dist, gMinDist[i][j] + gMinDist[ii][jj]);                     }                 }             }         }     }     return min_dist; } int main() {     int n, m, start_row, start_col;     scanf("%d %d", &n, &m);     memset(gMap, '#', sizeof(gMap));     memset(gMinDist, -1, sizeof(gMinDist));     for (int i = 1; i <= n; i++) {         getchar();         for (int j = 1; j <= m; j++) {             scanf("%c", &gMap[i][j]);             if (gMap[i][j] == 'H') {                 start_row = i;                 start_col = j;             }         }     }     Bfs(start_row, start_col);     int min_dist = MinDist(n, m);     if (min_dist == (1 << 29)) {         printf("Hi and Ho will not have lunch.\n");     }else         printf("%d\n", min_dist);     return 0; }