例题8-13 环形跑道（Just Finish it up, UVa 11093）

纸上模拟下，容易发现结论。

#include <set>#include <map>#include <ctime>#include <cmath>#include <stack>#include <queue>#include <deque>#include <cstdio>#include <string>#include <vector>#include <cctype>#include <sstream>#include <utility>#include <cstring>#include <cstdlib>#include <functional>#include <iostream>#include <algorithm>#define SF(a) scanf("%d", &a)#define PF(a) printf("%d\n", a)  #define SFF(a, b) scanf("%d%d", &a, &b)  #define SFFF(a, b, c) scanf("%d%d%d", &a, &b, &c)#define SFFFF(a, b, c, d) scanf("%d%d%d%d", &a, &b, &c, &d)#define CLEAR(a, b) memset(a, b, sizeof(a))#define IN() freopen("in.txt", "r", stdin)#define OUT() freopen("out.txt", "w", stdout)#define FOR(i, a, b) for(int i = a; i < b; ++i)#define LL long long#define maxn 100005#define maxm 205#define mod 1000000007#define INF 1000000007#define eps 1e-4using namespace std;int buf[20], l;int read() {int x = 0; char ch = getchar(); bool f = 0;while (ch < '0' || ch > '9') { if (ch == '-') f = 1; ch = getchar(); }while (ch >= '0' && ch <= '9') x = (x << 1) + (x << 3) + (ch ^ 48), ch = getchar();return f ? -x : x;}void write(int x) {if (!x) { putchar(48); return; }l = 0; if (x < 0) putchar('-'), x = -x;while (x) buf[++l] = x % 10, x = x / 10;while (l) putchar(buf[l--] + 48);}//-------------------------CHC------------------------------//int p[maxn], q[maxn], n;int check(int i) {int cnt = n;int sum = 0;bool last = false;while (cnt--) {sum += p[i] - q[i];if (sum < 0) {if(last) return -2;return i;}if ((i + 1) >= n) last = true;i = (i + 1) % n;}return -1;}int solve() {FOR(i, 0, n) {int res = check(i);if (res >= 0) i = res;else if (res == -1) return i;else break;}return -1;}int main() {int t, kase = 1;t = read();while (t--) {n = read();FOR(i, 0, n) p[i] = read();FOR(i, 0, n) q[i] = read();int ans = solve();printf("Case %d: ", kase++);if (ans < 0) puts("Not possible");else printf("Possible from station %d\n", ans + 1);}return 0;}