【HDOJ】1556 Color the ball

解法一：线段树, 延迟更新.

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
using namespace std;

#define MAXN 100001
#define lson l, mid, rt<<1
#define rson mid+1, r, rt<<1|1

int sum[MAXN<<2];
int delta[MAXN<<2];

void PushUp(int rt) {
    sum[rt] = sum[rt<<1] + sum[rt<<1|1];
}

void PushDown(int rt, int n) {
    if (delta[rt]) {
        delta[rt<<1] += delta[rt];
        delta[rt<<1|1] += delta[rt];
        sum[rt<<1] += delta[rt] * (n - (n>>1));
        sum[rt<<1|1] += delta[rt] * (n>>1);
        delta[rt] = 0;
    }
}

void build() {
    memset(sum, 0, sizeof(sum));
    memset(delta, 0, sizeof(delta));
}

void update(int ll, int rr, int l, int r, int rt) {
    if (ll<=l && rr>=r) {
        delta[rt]++;
        sum[rt] += r-l+1;
        return ;
    }
    PushDown(rt, r-l+1);
    int mid = (l+r)>>1;
    if (ll <= mid)
        update(ll, rr, lson);
    if (mid < rr)
        update(ll, rr, rson);
    PushUp(rt);
}

int query(int ll, int rr, int l, int r, int rt) {
    if (ll<=l && rr>=r) {
        return sum[rt];
    }
    PushDown(rt, r-l+1);
    int mid = (l+r)>>1, ret = 0;
    if (ll <= mid)
        ret += query(ll, rr, lson);
    if (mid < rr)
        ret += query(ll, rr, rson);
    return ret;
}

int main() {
    int n, a, b;
    int i, tmp;

    while (scanf("%d", &n)!=EOF && n) {
        build();
        for (i=0; i<n; ++i) {
            scanf("%d %d", &a, &b);
            update(a, b, 1, n, 1);
        }
        for (i=1; i<=n; ++i) {
            tmp = query(i, i, 1, n, 1);
            if (i != n)
                printf("%d ", tmp);
            else
                printf("%d
", tmp);
        }
    }

    return 0;
}

解法二：树状数组

#include <cstdio>
#include <cstring>

#define MAXN 100001

int sum[MAXN];
int n;

int lowbit(int x) {
    return x&(-x);
}

void update(int x, int delta) {
    while (x <= n) {
        sum[x] += delta;
        x += lowbit(x);
    }
}

int getSum(int x) {
    int ret = 0;
    while (x > 0) {
        ret += sum[x];
        x -= lowbit(x);
    }
    return ret;
}

int main() {
    int i, a, b;

    while (scanf("%d", &n)!=EOF && n) {
        memset(sum, 0, sizeof(sum));
        for (i=1; i<=n; ++i) {
            scanf("%d %d", &a, &b);
            update(a, 1);
            update(b+1, -1);
        }
        for (i=1; i<=n; ++i) {
            int tmp = getSum(i);
            if (i != n)
                printf("%d ", tmp);
            else
                printf("%d
", tmp);
        }
    }
    return 0;
}