POJ - 1661 Help Jimmy
input:
1 3 8 17 20 0 10 8 0 10 13 4 14 3
output:
23
分析:
dp。以从左下方上来为例,dp[i][0]=第i块阶梯从离i最近且合法的左下方阶梯过来的最短时间 dp[i][0]=block[i].h-block[k].h+min(dp[k][0]+block[i].l-block[k].l,dp[k][1]+block[k].r-block[i].l) 右下方同理。
code:
#define frp //#include<bits/stdc++.h> #include<cmath> #include<algorithm> #include<iostream> using namespace std; typedef long long ll; const ll INF = 0x3f3f3f3f; const ll inf = 0x7fffff; const int maxn = 1000; const int MAXN = 20050; struct node { int l, r, h; node(int x1 = 0, int x2 = 0, int height = 0) : l(x1), r(x2), h(height) {} bool operator<(const node &a) const { return h < a.h; } } block[MAXN]; int n, x, y, MAXH; int dp[MAXN][2]; bool inside(int x, int l, int r) { return x >= l && x <= r; } void turnLeftOrRight(int i, int j) { int k = i - 1; while (k > 0 && block[i].h - block[k].h <= MAXH) { if (j == 0 &&inside(block[i].l,block[k].l,block[k].r)) { dp[i][0] = block[i].h - block[k].h + min(dp[k][0] + block[i].l - block[k].l, dp[k][1] + block[k].r - block[i].l); return; } else if (j == 1 &&inside(block[i].r,block[k].l,block[k].r)) { dp[i][1] = block[i].h - block[k].h + min(dp[k][0] + block[i].r - block[k].l, dp[k][1] + block[k].r - block[i].r); return; } k--; } if (block[i].h - block[k].h <= MAXH) { dp[i][j] = block[i].h; } else { dp[i][j] = inf; } } void solve() { int t; cin >> t; while (t--) { cin >> n >> x >> y >> MAXH; block[0] = node(x, x, y); for (int i = 1; i < n + 1; i++) { int l, r, h; cin >> l >> r >> h; block[i] = node(l, r, h); } block[n + 1] = node(-inf, inf, 0); sort(block, block + n + 2); for (int i = 1; i <= n + 1; i++) { turnLeftOrRight(i, 0); turnLeftOrRight(i, 1); } cout << min(dp[n + 1][0], dp[n + 1][1]) << endl; } } int main() { ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); #ifdef frp freopen("D:\\coding\\c_coding\\in.txt", "r", stdin); // freopen("D:\\coding\\c_coding\\out.txt", "w", stdout); #endif solve(); return 0; }