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题目：Floyd算法
题目链接：
97. 小明逛公园 (kamacoder.com)
代码：
#include<bits/stdc++.h>
using namespace std;
struct Edge {int to;int val;Edge(int t, int w) :to(t), val(w) {}
};
int main() {int n, m;cin >> n >> m;int p1, p2, val;vector<vector<vector<int>>>grid(n + 1, vector<vector<int>>(n + 1, vector<int>(n + 1, 10005)));for (int i = 0; i < m; i++) {cin >> p1 >> p2 >> val;grid[p1][p2][0] = val;grid[p2][p1][0] = val;}for (int k = 1; k <= n; k++) {for (int i = 1; i <= n; i++) {for (int j = 1; j <= n; j++) {grid[i][j][k] = min(grid[i][j][k - 1], grid[i][k][k - 1] + grid[k][j][k - 1]);}}}int z, start, end;cin >> z;while (z--) {cin >> start >> end;if (grid[start][end][n] == 10005) cout << -1 << endl;else cout << grid[start][end][n] << endl;}
}题目：A*算法
题目链接：
127. 骑士的攻击 (kamacoder.com)
代码：
#include<bits/stdc++.h>
using namespace std;
int moves[1001][1001];
int dir[8][2] = { -2,-1,-2,1,-1,2,1,2,2,1,2,-1,1,-2,-1,-2 };
int b1, b2;
struct Knight {int x, y;int g, h, f;bool operator < (const Knight& k) const {return k.f < f;}
};
priority_queue<Knight>que;
int Heuristic(const Knight& k) {return (k.x - b1) * (k.x - b1) + (k.y - b2) * (k.y - b2);
}
void astar(const Knight& k) {Knight cur, next;que.push(k);while (!que.empty()) {cur = que.top();que.pop();if (cur.x == b1 && cur.y == b2) {break;}for (int i = 0; i < 8; i++) {next.x = cur.x + dir[i][0];next.y = cur.y + dir[i][1];if (next.x < 1 || next.x>1000 || next.y < 1 || next.y>1000) continue;if (!moves[next.x][next.y]) {moves[next.x][next.y] = moves[cur.x][cur.y] + 1;next.g = cur.g + 5;next.h = Heuristic(next);next.f = next.g + next.h;que.push(next);}}}
}
int main()
{int n, a1, a2;cin >> n;while (n--) {cin >> a1 >> a2 >> b1 >> b2;memset(moves, 0, sizeof(moves));Knight start;start.x = a1;start.y = a2;start.g = 0;start.h = Heuristic(start);start.f = start.g + start.h;astar(start);while (!que.empty()) que.pop(); // 队列清空cout << moves[b1][b2] << endl;}return 0;
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