本文共 2924 字，大约阅读时间需要 9 分钟。
会了GSS1，GSS3就比较无脑了
直接加个单点修改即可，然后update一下
/**/#include #include #include #include #include #include #include #include #include #include #define Pair pair #define MP(x, y) make_pair(x, y)#define fi first#define se second//#define int long long #define LL long long #define rg register #define sc(x) scanf("%d", &x);#define pt(x) printf("%d ", x);#define db(x) double x #define rep(x) for(int i = 1; i <= x; i++)//#define getchar() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1<<22, stdin), p1 == p2) ? EOF : *p1++)char buf[(1 << 22)], *p1 = buf, *p2 = buf;char obuf[1<<24], *O = obuf;#define OS *O++ = '\n';using namespace std;using namespace __gnu_pbds;const int MAXN = 50001, INF = 1e9 + 10, mod = 1e9 + 7;const double eps = 1e-9;inline int read() { char c = getchar(); int x = 0, f = 1; while(c < '0' || c > '9') { if(c == '-') f = -1; c = getchar();} while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar(); return x * f;}void print(int x) { if(x > 9) print(x / 10); *O++ = x % 10 + '0';}#define ls k << 1#define rs k << 1 | 1int N, M;int a[MAXN];struct Node { int l, r, lmx, rmx, mx, sum;}T[MAXN << 2];void update(int k) { T[k].sum = T[ls].sum + T[rs].sum; T[k].mx = max(T[ls].mx, T[rs].mx); T[k].mx = max(T[k].mx, T[ls].rmx + T[rs].lmx); T[k].rmx = max(T[rs].rmx, T[rs].sum + T[ls].rmx); T[k].lmx = max(T[ls].lmx, T[ls].sum + T[rs].lmx);}void Build(int k, int ll, int rr) { T[k] = (Node) {ll, rr, 0, 0, 0}; if(ll == rr) { T[k].lmx = T[k].rmx = T[k].mx = T[k].sum = a[ll]; return ; } int mid = ll + rr >> 1; Build(ls, ll, mid); Build(rs, mid + 1, rr); update(k);}Node merge(Node a, Node b) { Node now; now.sum = a.sum + b.sum; now.mx = max(a.mx, b.mx); now.mx = max(now.mx, a.rmx + b.lmx); now.rmx = max(b.rmx, b.sum + a.rmx); now.lmx = max(a.lmx, a.sum + b.lmx); // printf("%d %d %d %d\n", now.mx, now.lmx, now.rmx, now.sum); return now;}Node Query(int k, int ll, int rr) { Node ans = (Node) { 0, 0, 0, 0, 0}; if(ll <= T[k].l && T[k].r <= rr) return T[k]; int mid = T[k].l + T[k].r >> 1; /*if(ll <= mid) ans = Query(ls, ll, rr); if(rr > mid) ans = merge(ans, Query(rs, ll, rr));*/ if(ll > mid) return Query(rs, ll, rr); else if(rr <= mid) return Query(ls, ll, rr); else return merge(Query(ls, ll, rr), Query(rs, ll, rr)); return ans;}void PointChange(int k, int pos, int val) { if(T[k].l == T[k].r) { T[k].lmx = T[k].rmx = T[k].mx = T[k].sum = val; return ; } int mid = T[k].l + T[k].r >> 1; if(pos <= mid) PointChange(ls, pos, val); if(pos > mid) PointChange(rs, pos, val); update(k);}main() { //freopen("a.in", "r", stdin); N = read(); for(int i = 1; i <= N; i++) a[i] = read(); Build(1, 1, N); int M = read(); while(M--) { int opt = read(), x = read(), y = read(); if(opt == 1) printf("%d\n", Query(1, x, y).mx); else PointChange(1, x, y); } //fwrite(obuf, O-obuf, 1 , stdout); return 0;}/*5-10 12 1 -45 13451 52 34 51 43 5*/
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