World is Exploding

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解法：先求出所有Aa

#include <iostream>#include <stdio.h>#include <stdlib.h>#include <math.h>#include <algorithm>#include <string.h>using namespace std;struct Node{    int id, val;    bool operator>(Node &t) {        return val>t.val;    }    bool operator<(Node &t) {        return val<t.val;    }};const int maxn = 60000;long long fb[maxn], fs[maxn], bb[maxn], bs[maxn], f[maxn], b[maxn];Node a[maxn];int n;void insertb(int x) {    while (1) {        f[x] = f[x]+1;        if (x <= 1) break;        x = x-(x & (-x));    }}int findb(int x) {    int count = 0;    while (1) {        count = count+f[x];        x = x+(x & (-x));        if (x > n) break;    }    return count;}void inserts(int x) {    while (1) {        f[x] = f[x]+1;        x = x+(x & (-x));        if (x > n) break;    }}int finds(int x) {    int count = 0;    while (1) {        count = count+f[x];        if (x <= 1) break;        x = x-(x & (-x));    }    return count;}int main() {    int tt;    while ((scanf("%d", &n)) != EOF) {        for (int i = 1; i <= n; i++) {            scanf("%d", &a[i].val);            a[i].id = i;        }        sort(a+1, a+1+n);        int count = 1;        b[a[1].id] = 1;        for (int i = 2; i <= n; i++) {            if (a[i].val != a[i-1].val) count++;            b[a[i].id] = count;        }        memset(fb, 0, sizeof(fb));        memset(fs, 0, sizeof(fs));        memset(bb, 0, sizeof(bb));        memset(bs, 0, sizeof(bs));        memset(f, 0, sizeof(f));        for (int i = 1; i <= n; i++) {            insertb(b[i]);            fb[i] = findb(b[i]+1);        }        memset(f, 0, sizeof(f));        for (int i = n; i >= 1; i--) {            insertb(b[i]);            bb[i] = findb(b[i]+1);        }        memset(f, 0, sizeof(f));        for (int i = 1; i <= n; i++) {            inserts(b[i]);            fs[i] = finds(b[i]-1);        }        memset(f, 0, sizeof(f));        for (int i = n; i >= 1; i--) {            inserts(b[i]);            bs[i] = finds(b[i]-1);        }        long long ans = 0, /*bb*/temp1 = 0, /*bs*/temp2 = 0;        for (int i = 1; i <= n; i++) {            temp1 += bb[i];            temp2 += bs[i];        }        ans = temp1*temp2;        for (int i = 1; i <= n; i++) {            ans = ans-(fs[i]*bs[i]);            ans = ans-(bb[i]*bs[i]);            ans = ans-(fs[i]*fb[i]);            ans = ans-(fb[i]*bb[i]);        }        printf("%lld\n", ans);    }}