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https://www.luogu.org/problemnew/show/P1083

二分第i天不满足

前缀和 + 差分判断

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;
const int N = 1000010;

int n, m, ans;
int a[N], d[N], x[N], y[N], s[N], sum;

inline int read(){
    int x = 0; char c = getchar();
    while(c < '0' || c > '9') c = getchar();
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x;
}

inline bool judge(int v){
    memset(s, 0, sizeof(s));
    sum = 0;
    for(int i = 1; i <= v; i ++)
    {
        s[x[i]] += d[i];
        s[y[i]+1] -= d[i];
    }
    for(int i = 1; i <= n; i ++)
    {
        sum += s[i];
        if(sum > a[i]) return 0;
    }
    return 1;
}

int main()
{
    n = read();
    m = read();
    for(int i=1; i<=n; i++) a[i] = read();
    for(int i=1; i<=m; i++) d[i] = read(), x[i] = read(), y[i] = read();
    int l = 1, r = m;
    while(l <= r){
        int mid = (l + r) >> 1;
        if(!judge(mid)) ans = mid, r = mid - 1;
        else l = mid + 1;
    }
    if(!ans) printf("0");
    else printf("-1
%d",ans);
    return 0;
}