poj2823 Sliding Window

http://poj.org/problem?id=2823

单调队列：

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 1e6 + 10;
int a[maxn];
int n, k;
int mqx[maxn], idx[maxn], frontx, rearx;//monotone queue
int mqy[maxn], idy[maxn], fronty, reary;
int ax[maxn], ay[maxn], k1;

void solve(){
    frontx = fronty = 0;
    rearx = reary = 0;
    //head closed & tail open interval
    for(int i = 1; i <= k; i++){
        while(rearx > frontx && mqx[rearx - 1] <= a[i]) --rearx;
        mqx[rearx++] = a[i];
        idx[rearx - 1] = i;
        while(reary > fronty && mqy[reary - 1] >= a[i]) --reary;
        mqy[reary++] = a[i];
        idy[reary - 1]  = i;
    }
    k1 = 0;
    ax[k1] = mqx[frontx], ay[k1++] = mqy[fronty];
    for(int i = k + 1; i <= n; i++){
        int tail = i - k + 1;
        while(rearx  > frontx && mqx[rearx - 1] <= a[i]) --rearx;
        mqx[rearx++] = a[i];
        idx[rearx - 1] = i;
        while(idx[frontx] < tail){
            ++frontx;
        }
        while(reary > fronty && mqy[reary - 1] >= a[i]) --reary;
        mqy[reary++] = a[i];
        idy[reary - 1] = i;
        while(idy[fronty] < tail) ++fronty;
        ax[k1] = mqx[frontx];
        ay[k1++] = mqy[fronty];
    }
    printf("%d", ay[0]);
    for(int i = 1; i < k1; i++) printf(" %d", ay[i]);
    printf("
");
    printf("%d", ax[0]);
    for(int i = 1; i < k1; i++) printf(" %d", ax[i]);
    printf("
");
}

int main(){
    //freopen("in.txt", "r", stdin);
    while(~scanf("%d%d", &n, &k)){
        for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
        solve();
    }
    return 0;
}

堆维护：

（代码写得有些冗余了）

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 1e6 + 10;
int n, k;
int a[maxn];
int hx[maxn], idx[maxn], cidx[maxn];
int hy[maxn], idy[maxn], cidy[maxn];
int ax[maxn], ay[maxn], k1;

void swap(int &a, int &b) { int tem = b; b = a; a = tem; }

void adjx_down(int pos){
    int pi = pos << 1;
    while(pi <= k){
        //until reach the boundary
        if(pi < k && hx[pi + 1] > hx[pi]) ++pi;
        //point to the larger subnode
        if(hx[pi] <= hx[pi >> 1]) break;
        //right place to insert
        swap(hx[pi], hx[pi >> 1]);
        swap(idx[cidx[pi]], idx[cidx[pi >> 1]]);
        swap(cidx[pi], cidx[pi >> 1]);
        //push up node pi(swap with fa(pi))
        pi <<= 1;
        //continue comparsion
    }
}

void adjy_down(int pos){
    int pi = pos << 1;
    while(pi <= k){
        if(pi < k && hy[pi + 1] < hy[pi]) ++pi;
        if(hy[pi] >= hy[pi >> 1]) break;
        swap(hy[pi], hy[pi >> 1]);
        swap(idy[cidy[pi]], idy[cidy[pi >> 1]]);
        swap(cidy[pi], cidy[pi >> 1]);
        pi <<= 1;
    }
}

void adjx_up(int pos){
    int pi = pos;
    while(pi != 1 && hx[pi >> 1] < hx[pi]){
        swap(hx[pi], hx[pi >> 1]);
        swap(idx[cidx[pi]], idx[cidx[pi >> 1]]);
        swap(cidx[pi], cidx[pi >> 1]);
        pi >>= 1;
    }
}

void adjy_up(int pos){
    int pi = pos;
    while(pi != 1 && hy[pi >> 1] > hy[pi]){
        swap(hy[pi], hy[pi >> 1]);
        swap(idy[cidy[pi]], idy[cidy[pi >> 1]]);
        swap(cidy[pi], cidy[pi >> 1]);
        pi >>= 1;
    }
}

void init(){
    for(int i = 1; i <= k; i++) hy[i] = hx[i] = a[i], idy[i] = cidy[i] = idx[i] = cidx[i] = i;
    //idx :: pos in current array -> pos in hx
    //cidx :: pos in hx -> pos in the current array
    for(int i = k >> 1; i >= 1; i--) adjx_down(i), adjy_down(i);
}

void insertx(int num, int p, int pos){
    cidx[pos] = p;
    idx[p] = pos;
    hx[pos] = num;
    if(pos != 1 && num > hx[pos >> 1]) adjx_up(pos);
    else adjx_down(pos);
}

void inserty(int num, int p, int pos){
    cidy[pos] = p;
    idy[p] = pos;
    hy[pos] = num;
    if(pos != 1 && num < hy[pos >> 1]) adjy_up(pos);
    else adjy_down(pos);
}

void solve(){
    //the problem is how to delete the oldest element
    //easy to init and insert
    init();
    k1 = 0;
    ay[k1] = hy[1];
    ax[k1++] = hx[1];
    for(int i = k + 1; i <= n; i++){
        inserty(a[i], i, idy[i - k]);
        insertx(a[i], i, idx[i - k]);
        ay[k1] = hy[1];
        ax[k1++] = hx[1];
    }
    for(int i = 0; i < k1 - 1; i++) printf("%d ", ay[i]);
    printf("%d
", ay[k1 - 1]);
    for(int i = 0; i < k1 - 1; i++) printf("%d ", ax[i]);
    printf("%d
", ax[k1 - 1]);
}

int main(){
    //freopen("in.txt", "r", stdin);
    while(~scanf("%d%d", &n, &k)){
        for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
        solve();
    }
    return 0;
}