UVA 10881 - Piotr's Ants(等效变换)

Problem D
Piotr's Ants
Time Limit: 2 seconds

"One thing is for certain: there is no stopping them;
the ants will soon be here. And I, for one, welcome our
new insect overlords."

Kent Brockman

Piotr likes playing with ants. He has n of them on a horizontal pole L cm long. Each ant is facing either left or right and walks at a constant speed of 1 cm/s. When two ants bump into each other, they both turn around (instantaneously) and start walking in opposite directions. Piotr knows where each of the ants starts and which direction it is facing and wants to calculate where the ants will end up T seconds from now.

Input
The first line of input gives the number of cases, NN test cases follow. Each one starts with a line containing 3 integers: L , T and n (0 <= n <= 10000). The next n lines give the locations of the n ants (measured in cm from the left end of the pole) and the direction they are facing (L or R).

Output
For each test case, output one line containing "Case #x:" followed by n lines describing the locations and directions of the n ants in the same format and order as in the input. If two or more ants are at the same location, print "Turning" instead of "L" or "R" for their direction. If an ant falls off the pole before Tseconds, print "Fell off" for that ant. Print an empty line after each test case.

Sample Input Sample Output
2
10 1 4
1 R
5 R
3 L
10 R
10 2 3
4 R
5 L
8 R
Case #1:
2 Turning
6 R
2 Turning
Fell off

Case #2:
3 L
6 R
10 R

题意:给定一根柱子上的蚂蚁,和她们开始方向和爬行时间,蚂蚁相遇会碰头调转。问最后蚂蚁的位置。

思路:蚂蚁的相对位置是不变的,第i个位置的蚂蚁最后还是在第i个位置。如此一来只要记录下蚂蚁的最终位置,最后在判断状态按一定顺序输出即可

代码:

#include 
#include 
#include 
#include 
using namespace std;
const int M = 10005;

int t, l, time, m, out[M];
map vis;

struct Ant {
	int pos;
	char way[15];
	int num;
} ans[M];

int cmp(Ant a, Ant b) {
	return a.pos < b.pos;
}

void init() {
	int i;
	vis.clear();
	scanf("%d%d%d", &l, &time, &m);
	for (i = 0; i < m; i ++) {
		ans[i].num = i;
		scanf("%d%s", &ans[i].pos, ans[i].way);
	}
	sort(ans, ans + m, cmp);
	for (i = 0; i < m; i ++) {
		out[ans[i].num] = i;
		if (ans[i].way[0] == 'R') {
			ans[i].pos += time;
			vis[ans[i].pos] ++;
		}
		else {
			ans[i].pos -= time;
			vis[ans[i].pos] ++;
		}
	}
}

void solve() {
	sort(ans, ans + m, cmp);
	for (int j = 0; j < m; j ++) {
		int i = out[j];

		if (ans[i].pos < 0 || ans[i].pos > l) {
			printf("Fell off\n");
			continue;
		}
		printf("%d ", ans[i].pos);
		if (vis[ans[i].pos] >= 2)
			printf("Turning\n");
		else
			printf("%s\n", ans[i].way);
	}
	printf("\n");
}

int main() {
	scanf("%d", &t);
	int cas = 0;
	while (t--) {
		init();
		printf("Case #%d:\n", ++cas);
		solve();
	}
	return 0;
}


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