Codeforces 754A Lesha and array splitting (搜索)

题目链接 Lesha and array splitting

设s[i][j]为序列i到j的和，当s[i][j]≠0时，即可从i跳到j+1.目标为从1跳到n+1，所以按照题意暴力即可。

#include <bits/stdc++.h>

using namespace std;


#define rep(i,a,b)              for(int i(a); i <= (b); ++i)
#define dec(i,a,b)              for(int i(a); i >= (b); --i)

const int Q     =    1000        +       10;

struct node{
    int x, y;
} ans[Q];
int s[Q][Q];
int a[Q];

bool flag = false;
int n;
int sum;

void print(int x){
    printf("YES
%d
", x);
    rep(i, 1, x) printf("%d %d
", ans[i].x, ans[i].y);
}

void dfs(int x, int step){

    if (flag) return;
    if (x == n + 1){
        flag = true;
        print(step - 1);
        return;
    }

    dec(i, n, x) if (s[x][i]){
        ans[step].x = x, ans[step].y = i;
        dfs(i + 1, step + 1);
    }
}    

int main(){

    scanf("%d", &n);
    rep(i, 1, n) scanf("%d", a + i);
    rep(i, 1, n){
        sum = 0;
        rep(j, i, n){
            sum += a[j];
            s[i][j] = sum;
        }
    }

    dfs(1, 1);
    if (!flag) puts("NO");
    
    return 0;

}