Create 1661_jdplus.cpp

POJ/1661_jdplus.cpp

@@ -0,0 +1,97 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAXN 1010
+#define INF 9000000
+
+typedef struct platform{
+	int x1;
+	int x2;
+	int high;
+}Platform;
+
+int compare (const void * p, const void * q){
+	Platform * p1 = (Platform *)p;
+	Platform * q1 = (Platform *)q;
+	return p1->high - q1->high;
+}
+
+int Min (int a, int b){
+	return (a < b) ? a : b;
+}
+
+int N, X, Y, MAX;
+Platform plat[MAXN];
+int dp[MAXN][2];         //dp[i][0]、dp[i][1]分别表示从第i个平台左、右边到地面的最短时间
+
+void LeftMinTime (int i){    //计算从平台i左边到地面的最短时间
+	int k = i - 1;
+	while (k > 0 && plat[i].high - plat[k].high <= MAX){
+		//如果平台i左边下面有平台，且两者相距不超过MAX
+		if (plat[i].x1 >= plat[k].x1 && plat[i].x1 <= plat[k].x2){
+			dp[i][0] = plat[i].high - plat[k].high + 
+				Min (plat[i].x1 - plat[k].x1 + dp[k][0], plat[k].x2 - plat[i].x1 + dp[k][1]);
+			return;
+		}
+		else
+			--k;
+	}
+	//如果平台i左边下面没有平台，或者两者相距超过了MAX
+	if (plat[i].high - plat[k].high > MAX)
+		dp[i][0] = INF;
+	else
+		dp[i][0] = plat[i].high;
+}
+
+void RightMinTime (int i){   //计算从平台i右边到地面的最短时间
+	int k = i - 1;
+	while (k > 0 && plat[i].high - plat[k].high <= MAX){
+		//如果平台i右边下面有平台，且两者相距不超过MAX
+		if (plat[i].x2 >= plat[k].x1 && plat[i].x2 <= plat[k].x2){
+			dp[i][1] = plat[i].high - plat[k].high + 
+				Min (plat[i].x2 - plat[k].x1 + dp[k][0], plat[k].x2 - plat[i].x2 + dp[k][1]);
+			return;
+		}
+		else
+			--k;
+	}
+	//如果平台i右边下面没有平台，或者两者相距超过了MAX
+	if (plat[i].high - plat[k].high > MAX)
+		dp[i][1] = INF;
+	else
+		dp[i][1] = plat[i].high;
+}
+
+int ShortestTime (){
+	int i, j;
+
+	for (i=1; i<=N+1; ++i){
+		LeftMinTime (i);
+		RightMinTime (i);
+	}
+	return Min (dp[N+1][0], dp[N+1][1]);
+}
+
+int main(void){
+	int t;
+	int i;
+	while (scanf ("%d", &t) != EOF){
+		while (t-- != 0){
+			scanf ("%d%d%d%d", &N, &X, &Y, &MAX);
+			for (i=1; i<=N; ++i){
+				scanf ("%d%d%d", &plat[i].x1, &plat[i].x2, &plat[i].high);
+			}
+			plat[0].high = 0;
+			plat[0].x1 = -20000;
+			plat[0].x2 = 20000;
+			plat[N+1].high = Y;
+			plat[N+1].x1 = X;
+			plat[N+1].x2 = X;
+			//根据平台高度按从低到高排序
+			qsort (plat, N+2, sizeof(Platform), compare);
+			printf ("%d\n", ShortestTime());
+		}
+	}
+
+	return 0;
+}