hdu 5183 Negative and Positive （前缀和加强版，强数据。。）

题意：
。。。
思路：
恩。
这道题数据太强了，以至于不用输入挂过不了 = =
我是用的输入挂+hash

int t, n, k;LL a[Maxn+5], f[2][Maxn+5];const int Mod = (int)(1e6+7);struct Ent{    LL val;    int nxt;};Ent buffer[Mod*2+5];int head[Mod+5], tot;void read(LL &x) {    char ch = getchar();    LL tag = 1;    x = 0;    while ((ch < '0' || ch > '9') && ch != '-') {        ch = getchar();    }    if (ch == '-') {        tag = -1;        ch = getchar();    }    while (ch >= '0' && ch <= '9') {        x = x * 10 + ch - 48;        ch = getchar();    }    x *= tag;}inline int Find(LL k) {    int key = k % Mod;    if (key < 0) key += Mod;    for (int i=head[key];i!=-1;i=buffer[i].nxt) {        if (buffer[i].val == k) return 1;    }    return 0;}inline void Add(LL k) {    //if (Find(k)) return;    int key = k % Mod;    if (key < 0) key += Mod;    buffer[tot++] = (Ent){k, head[key]};    head[key] = tot-1;}int main() {#ifndef ONLINE_JUDGE    freopen("input.in", "r", stdin);#endif    SPEED_UP    scanf("%d", &t);    LL x;    rep(kase, 1, t) {        scanf("%d%d", &n, &k);        //printf("d: %d\n", n);        LL K = k;        f[0][0] = f[1][0] = 0;        //map<LL, int> m1, m2;        tot = 0;memset(head, -1, sizeof(head));        int ok = 0;        rep(i, 1, n) //scanf("%I64d", a+i);        {            if (i<n) read(a[i]);            else scanf("%I64d", a+i);        }        rep(i, 1, n) {            LL x = a[i];            if (i&1) {                f[0][i] = f[0][i-1]+x;                f[1][i] = f[1][i-1]-x;            }            else {                f[0][i] = f[0][i-1]-x;                f[1][i] = f[1][i-1]+x;            }            //printf("input %I64d: \n", x);            //printf("%I64d, %I64d\n", f[0][i], f[1][i]);            //if (m1[f[0][i]-K] > 0) {            if (Find(f[0][i]-K)) {                //printf("found: %I64d\n", f[0][i]-k*1ll);                ok = 1;break;            }            //if (m2[f[1][i]-K] > 0) {            if (Find(f[1][i]-K)) {                //printf("found: %I64d\n", f[1][i]-k*1ll);                ok = 1;break;            }            if (i&1) Add(f[1][i]);//m2[f[1][i]] += 1;            else Add(f[0][i]);//m1[f[0][i]] += 1;            if (f[0][i] == k) {                ok = 1;break;            }        }        printf("Case #%d: ",kase);        if (ok) puts("Yes.");        else puts("No.");    }    return 0;}

再收藏一个神牛的代码

#include <stdio.h>#include <stdlib.h>#include <iostream>#include <algorithm>#include <cstring>#define Max(a, b) ((FASTBUFFER = ((a) - (b)) >> 31), ((b) & FASTBUFFER | (a) & ~FASTBUFFER))#define Min(a, b) ((FASTBUFFER = ((a) - (b)) >> 31), ((a) & FASTBUFFER | (b) & ~FASTBUFFER))#define Swap(a, b) (a ^= b, b ^= a, a ^= b)#define OO 2147483647#define priority_queue PQusing namespace std;int FASTBUFFER;const int N = 1000005;int test;void read(int &x) {    char ch = getchar();    int tag = 1;    x = 0;    while ((ch < '0' || ch > '9') && ch != '-') {        ch = getchar();    }    if (ch == '-') {        tag = -1;        ch = getchar();    }    while (ch >= '0' && ch <= '9') {        x = x * 10 + ch - 48;        ch = getchar();    }    x *= tag;}int n, k, hashTag, hashNow[N];long long s[N], temp[N];void work() {    scanf("%d %d", &n, &k);    for (int i = 1; i <= n; i++) {        int x;        if (i == n) {            scanf("%d", &x);        } else {            read(x);        }        if (i & 1) {            s[i] = s[i - 1] + x;        } else {            s[i] = s[i - 1] - x;        }        temp[i] = s[i];    }    sort(temp + 1, temp + n + 1);    int tot = unique(temp + 1, temp + n + 1) - temp - 1;    hashTag++;    for (int i = n; i >= 0; i--) {        long long need;        if (i & 1) {            need = -((long long)k - s[i]);        } else {            need = s[i] + k;        }        long long *xx = lower_bound(temp + 1, temp + n + 1, need);        if (*xx == need && hashNow[xx - temp] == hashTag) {            printf("Yes.\n");            return;        }        hashNow[lower_bound(temp + 1, temp + n + 1, s[i]) - temp] = hashTag;    }    printf("No.\n");}int tt;int main() {    //freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);    scanf("%d", &test);    while (test--) {        printf("Case #%d: ", ++tt);        work();    }    return 0;}