75 lines
2.4 KiB
C
75 lines
2.4 KiB
C
#include <stdio.h>
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struct node {
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long from, to;
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long value;
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};
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int build_tree(struct node *tree,int *stations, long idx, long from, long to);
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long find_section(struct node *tree, long idx, long from, long to);
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int upd_point(struct node * tree, long idx, long p_idx, long value);
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#define MAX (200000+5)
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int students[MAX];
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struct node tree[4*MAX];
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int main(void) {
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long sn, cn, i;
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while(scanf("%ld %ld",&sn,&cn) != EOF){
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for(i = 0; i < sn; i++) scanf("%d",students+i);
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build_tree(tree, students, 0, 1, sn);
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for(i = 0; i < cn; i++){
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char cmd[2];
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scanf("%s",cmd);
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if(cmd[0] == 'Q'){
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long fidx, tidx;
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scanf("%ld %ld",&fidx,&tidx);
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printf("%ld\n",find_section(tree, 0,fidx, tidx));
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}
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else if(cmd[0] == 'U'){
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long idx;
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int value;
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scanf("%ld %d",&idx,&value);
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upd_point(tree, 0, idx, value);
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}
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}
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}
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return 0;
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}
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int build_tree(struct node *tree,int *students, long idx, long from, long to){
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tree[idx].from = from;
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tree[idx].to = to;
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if(from < to){
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build_tree(tree, students, 2*idx+1, from, (from+to)/2);
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build_tree(tree, students, 2*idx+2, (from+to)/2+1, to);
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tree[idx].value = (tree[2*idx+1].value)>(tree[2*idx+2].value)?(tree[2*idx+1].value):(tree[2*idx+2].value);
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}
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else tree[idx].value = students[from-1];
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return 0;
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}
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long find_section(struct node *tree, long idx, long from, long to){
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long h_idx = (tree[idx].from + tree[idx].to)/2;
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if(tree[idx].from == from && tree[idx].to == to)
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return tree[idx].value;
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if(from <= h_idx && to > h_idx){
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long f = find_section(tree, idx*2+1, from, h_idx), s = find_section(tree, idx*2+2, h_idx+1, to);
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return f>s?f:s;
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}
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else if(from <= h_idx && to <= h_idx) return find_section(tree, idx*2+1, from, to);
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else if(from > h_idx && to > h_idx) return find_section(tree, idx*2+2, from, to);
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else return 0;
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}
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int upd_point(struct node * tree, long idx, long p_idx, long value){
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long h_idx = (tree[idx].from+tree[idx].to)/2;
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if(tree[idx].from < tree[idx].to){
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if(p_idx <= h_idx) upd_point(tree, idx*2+1, p_idx, value);
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else upd_point(tree, idx*2+2, p_idx, value);
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}
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if(tree[idx].value < value) tree[idx].value = value;
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return 0;
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}
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