鸽巢原理(入门优化) 之 poj 3370

解决方法同：请点击此处

在设计代码时，如还用上面方法， 1172ms

//  [3/27/2014 Sjm]
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <algorithm>
#include <queue>
using namespace std;

const int MAX_N = 100000;
int C, N;
struct node{
    int x, y; 
    friend bool operator < (const node &n1, const node &n2) {
        if (n1.y == n2.y) return n1.x > n2.x;
        else return n1.y > n2.y;
    }
};

void Solve(priority_queue<node> pri_que){
    node n1 = pri_que.top();
    pri_que.pop();
    while (pri_que.size())
    {
        node n2 = pri_que.top();
        pri_que.pop();
        if (n1.y == n2.y) {
            int myl = n1.x + 1, myr = n2.x;
            if (myl == myr) {
                printf("%d
", myl);
                return;
            }
            else {
                for (int i = myl; i <= myr; i++){
                    printf("%d", i);
                    if (i != myr) printf(" ");
                    else printf("
");
                }            
                return;
            }
        }
        n1 = n2;
    }
    printf("no sweets
");
}

int main(){
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    while (scanf("%d%d", &C, &N) && (C || N))
    {
        priority_queue<node> pri_que;
        node n1;
        n1.x = 0, n1.y = 0;
        pri_que.push(n1);
        int t, sum = 0;
        for (int i = 0; i < N; i++){
            scanf("%d", &t);
            sum = (sum + t) % C;
            n1.x = i + 1, n1.y = sum;
            pri_que.push(n1);
        }
        Solve(pri_que);
    }
    return 0;
}

优化方法，增加标记  flag[MAX_N] ，829ms:

//  [3/27/2014 Sjm]
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <vector>
using namespace std;

const int MAX_N = 100000;
int C, N, arr[MAX_N + 1];

void Solve(){
    int l = 0, r = 0, sum = 0;
    vector<int> flag(C, 0);
    for (int i = 1; i <= N; i++) {
        sum = (sum + arr[i]) % C;
        if (0 == sum) {
            l = 1;
            r = i;
            break;
        }
        else {
            if (flag[sum]) {
                l = flag[sum] + 1;
                r = i;
                break;
            }
            else flag[sum] = i;
        }
    }
    for (int i = l; i <= r; i++) {
        printf("%d", i);
        if (i != r) printf(" ");
        else printf("
");
    }
}

int main(){
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    while (scanf("%d%d", &C, &N) && (C || N))
    {
        for (int i = 1; i <= N; i++)
            scanf("%d", &arr[i]);
        Solve();
    }
    return 0;
}