POJ 3368 Frequent values 线段树

文字解释见 http://hi.baidu.com/lewutian/blog/item/d0e058ea85b780d8d539c9bf.html

/*ID: sdj22251PROG: subsetLANG: C++*/#include <iostream>#include <vector>#include <list>#include <map>#include <set>#include <deque>#include <queue>#include <stack>#include <bitset>#include <algorithm>#include <functional>#include <numeric>#include <utility>#include <sstream>#include <iomanip>#include <cstdio>#include <cmath>#include <cstdlib>#include <cctype>#include <string>#include <cstring>#include <cmath>#include <ctime>#define MAXN 111111#define MAXM 104444#define INF 100000000#define PI acos(-1.0)#define eps 1e-12#define L(X) X<<1#define R(X) X<<1|1using namespace std;struct PP{    int left, right, num;}p[MAXN];struct node{    int left, right, mid;    int mx;}tree[4 * MAXN];int v[MAXN], h[MAXN];int n, m, len;void get(){    len = 1;    p[1].left = 1;    p[1].num = 1;    h[1] = 1;    for(int i = 2; i <= n; i++)    {        if(v[i] == v[i - 1])        p[len].num++;        else        {            p[len++].right = i - 1;            p[len].left = i;            p[len].num = 1;        }        h[i] = len;    }    p[len].right = n;}void up(int C){    tree[C].mx = max(tree[L(C)].mx, tree[R(C)].mx);}void make_tree(int s, int e, int C){    tree[C].left = s;    tree[C].right = e;    tree[C].mid = (s + e) >> 1;    if(s == e){tree[C].mx = p[s].num; return;}    make_tree(s, tree[C].mid, L(C));    make_tree(tree[C].mid + 1, e, R(C));    up(C);}int query(int s, int e, int C){    if(tree[C].left >= s && tree[C].right <= e) return tree[C].mx;    int ret = 0;    if(tree[C].mid >= s) {int t = query(s, e, L(C)); ret = max(ret, t);}    if(tree[C].mid < e) {int t = query(s, e, R(C)); ret = max(ret, t);}    return ret;}int in(){    int flag = 1;    char ch;    int a = 0;    while((ch = getchar()) == ' ' || ch == '\n');    if(ch == '-') flag = -1;    else    a += ch - '0';    while((ch = getchar()) != ' ' && ch != '\n')    {        a *= 10;        a += ch - '0';    }    return flag * a;}void out(int a){    if(a < 0) {putchar('-'); a = -a;}    if(a >= 10)out(a / 10);    putchar(a % 10 + '0');}int main(){    while(scanf("%d", &n) != EOF && n)    {        scanf("%d", &m);        for(int i = 1; i <= n; i++) v[i] = in();        get();        make_tree(1, len, 1);        for(int i = 1; i <= m; i++)        {            int x, y;            x= in();            y = in();            int u = h[x];            int v = h[y];            if(u == v) out(y - x + 1);            else if(u == v - 1) out(max(p[u].right - x + 1, y - p[v].left + 1));            else            {                int ans = max(p[u].right - x + 1, y - p[v].left + 1);                int t = query(u + 1, v - 1, 1);                ans = max(ans, t);                out(ans);            }            putchar('\n');        }    }    return 0;}