hdu 3484 Interviewe RMQ+二分

#include <cstdio>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 200000 + 5;
int a[maxn];
int maxsum[maxn][30];
int n, k;

void RMQ(int num){
    for (int i = 1; i <= num; i++){
        maxsum[i][0] = a[i];
    }

    for (int j = 1; j < 30; j++){
        for (int i = 1; i <= num; i++){
            if (i + (1 << j) - 1 <= num){
                maxsum[i][j] = max(maxsum[i][j - 1], maxsum[i + (1 << (j - 1))][j - 1]);
            }
        }
    }
    return;
}

//获取[x,y]的最大值
int getmax(int x, int y){
    int k1 = (int)(log((double)(y - x + 1)) / log(2.0));
    return max(maxsum[x][k1], maxsum[y - (1 << k1) + 1][k1]);
}

//获取m人的最大值(m组)
int Find(int m){
    int ans = 0;
    int num = n / m;//每组num个人
    for (int i = 0; i < m; i++){
        ans += getmax(1 + i*num, (i + 1)*num);
        if (ans > k)
            return ans;
    }
    return ans;
}

int main(){
    while (~scanf("%d%d", &n, &k)){
        if (n == -1 && k == -1)
            break;
        int sum = 0;
        bool ok_1 = false;
        for (int i = 1; i <= n; i++){
            scanf("%d", &a[i]);
            if (a[i] > k){
                ok_1 = true;
            }
            sum += a[i];
        }
        if (ok_1){
            printf("1
");
            continue;
        }
        if (sum < k){
            printf("-1
");
            continue;
        }
        if (sum == k){
            printf("%d
", k);
            continue;
        }
        //初始化
        RMQ(n);
        bool ok = false;
        int l = 1;
        int r = n;
        int ans = 0;
        int mid, t;
        while (l <= r){
            mid = (l + r) / 2;
            t = Find(mid);
            if (t > k){
                r = mid - 1;
                ans = mid;
                ok = true;
            }
            else{
                l = mid + 1;
            }
        }
        if (ok)
            printf("%d
", ans);
        else
            printf("-1
");
    }
    //system("pause");
    return 0;
}