线段树，题目感觉比较难，看别人思路做的。还得继续练这个专题。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 using namespace std; 5 6 #define MAXN 100005 7 #define lson l, mid, rt<<1 8 #define rson mid+1, r, rt<<1|1 9 10 int str[MAXN<<2], lstr[MAXN<<2], rstr[MAXN<<2]; 11 int nums[MAXN]; 12 13 inline int mymax(int a, int b) { 14 return (a>b) ? a:b; 15 } 16 17 inline int mymin(int a, int b) { 18 return (a<b) ? a:b; 19 } 20 21 void PushUP(int l, int r, int rt) { 22 int mid; 23 24 str[rt] = mymax(str[rt<<1], str[rt<<1|1]); 25 lstr[rt] = lstr[rt<<1]; 26 rstr[rt] = rstr[rt<<1|1]; 27 28 mid = (l+r)>>1; 29 if (nums[mid] < nums[mid+1]) { 30 if (lstr[rt] == mid-l+1) 31 lstr[rt] += lstr[rt<<1|1]; 32 if (rstr[rt] == r-mid) 33 rstr[rt] += rstr[rt<<1]; 34 str[rt] = mymax(str[rt], lstr[rt<<1|1]+rstr[rt<<1]); 35 } 36 } 37 38 void build(int l, int r, int rt) { 39 int mid; 40 if (l == r) { 41 str[rt] = lstr[rt] = rstr[rt] = 1; 42 return ; 43 } 44 mid = (l+r)>>1; 45 build(lson); 46 build(rson); 47 PushUP(l, r, rt); 48 } 49 50 void update(int x, int c, int l, int r, int rt) { 51 int mid; 52 if (l == r) { 53 nums[x] = c; 54 return ; 55 } 56 mid = (l+r)>>1; 57 if (x <= mid) 58 update(x, c, lson); 59 else 60 update(x, c, rson); 61 PushUP(l, r, rt); 62 } 63 64 int query(int ll, int rr, int l, int r, int rt) { 65 int mid, ret = 0; 66 if (ll<=l && rr>=r) 67 return str[rt]; 68 69 mid = (l+r)>>1; 70 if (ll <= mid) 71 ret = mymax(ret, query(ll,rr,lson)); 72 if (rr > mid) 73 ret = mymax(ret, query(ll,rr,rson)); 74 75 if (ll<=mid && mid<rr && nums[mid]<nums[mid+1]) { 76 ret = mymax(ret, mymin(mid-ll+1,rstr[rt<<1])+mymin(lstr[rt<<1|1],rr-mid)); 77 } 78 79 return ret; 80 } 81 82 void output(int beg, int end) { 83 int i; 84 for (i=beg; i<end; ++i) 85 printf(" %d: l=%d,s=%d,w=%d ", i, lstr[i], rstr[i], str[i]); 86 } 87 88 int main() { 89 int case_n, n, m; 90 int i, x, y; 91 char cmd[3]; 92 93 scanf("%d", &case_n); 94 95 while (case_n--) { 96 scanf("%d %d", &n, &m); 97 for (i=0; i<n; ++i) 98 scanf("%d", &nums[i]); 99 build(0, n-1, 1); 100 while (m--) { 101 scanf("%s %d %d", cmd, &x, &y); 102 if (cmd[0] == 'Q') { 103 printf("%d ", query(x,y,0,n-1,1)); 104 } else { 105 update(x, y, 0, n-1, 1); 106 } 107 //output(1, 18); 108 } 109 } 110 111 return 0; 112 }