UVA10285 - Longest Run on a Snowboard

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题意：滑雪场各个点的高度是不一样的。滑雪时只能从高的滑向低的地方。求经过的最多能经过多少个点。

思路：无固定起点的DAG最长路

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int MAXN = 105;const int dx[] = {-1, 0, 0, 1};const int dy[] = {0, -1, 1, 0};char name[MAXN];int map[MAXN][MAXN], d[MAXN][MAXN];int r, c;int dp(int x, int y) {    int& ans = d[x][y];    if (ans > 0)        return ans;    ans = 1;    for (int i = 0; i < 4; i++) {        int tx = x + dx[i];         int ty = y + dy[i];        if (tx >= 0 && tx < r && ty >= 0 && ty < c && map[x][y] > map[tx][ty]) {             ans = max(ans, dp(tx, ty) + 1);         }     }    return ans;}int main() {    int cas;    scanf("%d", &cas);    while (cas--) {        scanf("%s %d %d", name, &r, &c);         for (int i = 0; i < r; i++)             for (int j = 0; j < c; j++)                scanf("%d", &map[i][j]);        memset(d, 0, sizeof(d));        int Max = 0;        for (int i = 0; i < r; i++)            for (int j = 0; j < c; j++) {                int num = dp(i, j);                 if (num >= Max)                     Max = num;            }        printf("%s: %d\n", name, Max);    }    return 0;}

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