HDU6205 card card card

思维

把数组扩大一倍，然后找连续的大于0的最长的一段即可，注意结尾特判一下。

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
#define full(a, b) memset(a, b, sizeof a)
#define FAST_IO ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
using namespace std;
typedef long long ll;
inline int lowbit(int x){ return x & (-x); }
inline int read(){
    int ret = 0, w = 0; char ch = 0;
    while(!isdigit(ch)) { w |= ch == '-'; ch = getchar(); }
    while(isdigit(ch)) ret = (ret << 3) + (ret << 1) + (ch ^ 48), ch = getchar();
    return w ? -ret : ret;
}
inline int gcd(int a, int b){ return b ? gcd(b, a % b) : a; }
inline int lcm(int a, int b){ return a / gcd(a, b) * b; }
template <typename T>
inline T max(T x, T y, T z){ return max(max(x, y), z); }
template <typename T>
inline T min(T x, T y, T z){ return min(min(x, y), z); }
template <typename A, typename B, typename C>
inline A fpow(A x, B p, C lyd){
    A ans = 1;
    for(; p; p >>= 1, x = 1LL * x * x % lyd)if(p & 1)ans = 1LL * x * ans % lyd;
    return ans;
}
const int N = 2000005;
int a[N], b[N], c[N], n;

int main(){

    while(~scanf("%d", &n)){
        for(int i = 1; i <= n; i ++) a[i] = read();
        for(int i = 1; i <= n; i ++) b[i] = read();
        for(int i = 1; i <= n; i ++) c[i] = a[i] - b[i];
        for(int i = n + 1; i <= 2 * n; i ++) c[i] = a[i - n] - b[i - n];
        int sum = 0, index = -1, maxi = -INF, ans = -1, len = 0;
        for(int i = 1; i <= 2 * n; i ++){
            if(index == -1 && c[i] < 0) continue;
            else if(index == -1) sum += c[i], index = i, len ++;
            else if(sum + c[i] >= 0){
                sum += c[i], len ++;
                if(i == 2 * n){
                    if(len > maxi) maxi = len, ans = index;
                }
            }
            else if(sum + c[i] < 0){
                if(len > maxi) maxi = len, ans = index;
                sum = 0, len = 0, index = -1;
            }
            if(maxi == n) break;
        }
        printf("%d
", ans - 1);
    }
    return 0;
}