【BZOJ1560】[JSOI2009]火星藏宝图【DP】

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【题目链接】

可以证明，如果有A->B->C，那么A->C一定不是最优的。然后搞一搞就行啦。

/* Telekinetic Forest Guard */#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 200005, maxm = 1005, inf = 0x3f3f3f3f;int n, m, dp[maxn], now[maxm];struct _point {int x, y, w;bool operator < (const _point &a) const {return y != a.y ? y < a.y : x < a.x;}} p[maxn];inline int iread() {int f = 1, x = 0; char ch = getchar();for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';return f * x;}inline int dis(_point &a, _point &b) {return (a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y);}int main() {n = iread(); m = iread();for(int i = 1; i <= n; i++) p[i].x = iread(), p[i].y = iread(), p[i].w = iread();sort(p + 1, p + 1 + n);memset(dp, -0x3f, sizeof(dp));dp[1] = p[1].w;for(int i = 1; i <= n; i++) {for(int j = 1; j <= p[i].x; j++) if(now[j])dp[i] = max(dp[i], dp[now[j]] - dis(p[now[j]], p[i]) + p[i].w);now[p[i].x] = i;}printf("%d\n", dp[n]);return 0;}

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