题目连接:10131 - Is Bigger Smarter?
题目大意:给出n只大象的属性, 包括重量w, 智商s, 现在要求找到一个连续的序列, 要求每只大象的重量比前一只的大, 智商却要小, 输出最长值和方案, 方案不唯一的时候任意输出一种。
解题思路:DAG无定点的最长路问题, 记忆化搜索,并记录当前最有解的前驱。
#include <stdio.h>
#include <string.h>
const int N = 10005; struct State {
int w;
int s;
}tmp[N];
int n, dp[N], vis[N]; int find(int cur) {
if (dp[cur]) return dp[cur];
int a;
vis[cur] = cur;
State& now = tmp[cur];
for (int i = 0; i < n; i++) {
if (tmp[i].w < now.w && tmp[i].s > now.s) {
a = find(i);
if (dp[cur] <= a) {
dp[cur] = a;
vis[cur] = i;
}
}
}
return ++dp[cur];
} void solve() {
int Max = 0, id = 0, ans[N], cnt = 0;
for (int i = 0; i < n; i++) {
if (!dp[i]) find(i);
if (Max < dp[i]) {
Max = dp[i];
id = i;
}
} printf("%d\n", Max);
while (id != vis[id]) {
ans[cnt++] = id + 1;
id = vis[id];
}
ans[cnt++] = id + 1; for (int i = cnt - 1; i >= 0; i--)
printf("%d\n", ans[i]); } int main() {
// Init;
n = 0;
memset(tmp, 0, sizeof(tmp));
memset(vis, 0, sizeof(vis));
memset(dp, 0, sizeof(dp)); // Read;
while(scanf("%d%d", &tmp[n].w, &tmp[n].s) == 2)
n++; solve(); return 0;
}