AOJ 351 rmq或 基础线段树 求解

题目链接：AOJ 351

RMQ:

#include<cstdio>#include<cstring>#include<algorithm>#include<queue>#include<cmath>using namespace std;#define debug 0 const int maxn = 100000 + 5;int a[maxn],n,m,Max[maxn][20],Min[maxn][20]; void initRMQ() {     for (int i = 1; i <= n; i++) {        Max[i][0] = Min[i][0] = a[i];    }     for(int j = 1; j < 20; j++)//初始化        for(int i = 1; i <= n; i++)            if (i + (1 << j) - 1 <= n)            {                Max[i][j] = max(Max[i][j - 1], Max[i + (1 << (j - 1))][j - 1]);                Min[i][j] = min(Min[i][j - 1], Min[i + (1 << (j - 1))][j - 1]);            }} int main() {#if debug    freopen("in.txt", "r", stdin);#endif//debug    int l, r;    while (~scanf("%d%d", &n, &m))    {        for (int i = 1; i <= n; i++)            scanf("%d", &a[i]);        initRMQ();        while (m--)        {            scanf("%d%d", &l, &r);            int x = (int)log2(r - l + 1);//query查询

            int maxAns = max(Max[l][x], Max[r - (1 << x) + 1][x]);            int minAns = min(Min[l][x], Min[r - (1 << x) + 1][x]);            printf("%d\n", maxAns - minAns);        }    }     return 0;}

线段树:

#include<cstdio>#include<cstring>#include<string>#include<algorithm>#include<stack>using namespace std;#define debug 0 const int maxn = 100000 + 5;int  Max[maxn << 2], Min[maxn << 2];int n, m, ans1, ans2;#define Mid ((l + r) >> 1)#define ls  rt << 1, l , Mid#define rs  rt << 1 | 1, Mid + 1 , rvoid build(int rt, int l, int r) {     if (l == r){        scanf("%d", &Max[rt]);//建树时读入        Min[rt] = Max[rt];    }else {        build(rt << 1, l, (l + r) >> 1);        build(rt << 1 | 1, ((l + r) >> 1) + 1, r);        Max[rt] = max(Max[rt << 1], Max[rt << 1 | 1]);        Min[rt] = min(Min[rt << 1], Min[rt << 1 | 1]);    }} void  query(int rt, int l, int r, int L, int R) {//查询     if (L <= l && r <= R) {        ans1 = max(ans1, Max[rt]);        ans2 = min(ans2, Min[rt]);    }else {        if (L <= ((l + r) >> 1)){            query(ls, L, R);        }        if (R > ((l + r) >> 1)) {            query(rs, L, R);        }    }} int main() {#if debug    freopen("in.txt", "r", stdin);#endif //debug    int a, b;    while (~scanf("%d%d", &n, &m)) {        build(1, 1, n);        while (m--) {            ans1 = -0x3f3f3f3f;            ans2 = 0x3f3f3f3f;            //printf("%d\n", m);            scanf("%d%d", &a, &b);            query(1, 1, n, a, b);             printf("%d\n", ans1 - ans2);        }     }     return 0;}