先把所有区间按照左端点排序
f[i]表示区间0~i的最优解
#include <cstdio> #include <iostream> #include <algorithm> #define max(x, y) ((x) > (y) ? (x) : (y)) int n, v; int f[3000001]; struct node { int x, y; }p[150001]; inline int read() { int x = 0, f = 1; char ch = getchar(); for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1; for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0'; return x * f; } inline bool cmp(node a, node b) { return a.x < b.x; } int main() { int i, j = 1; n = read(); for(i = 1; i <= n; i++) p[i].x = read(), p[i].y = read(), v = max(v, p[i].y); std::sort(p + 1, p + n + 1, cmp); for(; !p[j].x; j++) f[p[j].y] = p[j].y + 1; for(i = 1; i <= v; i++) { f[i] = max(f[i], f[i - 1]); for(; p[j].x == i; j++) f[p[j].y] = max(f[p[j].y], f[i - 1] + p[j].y - p[j].x + 1); } printf("%d ", f[v]); return 0; }